Francesca Tonolo- Molecular Physics Department, Institut de Physique de Rennes, University of Rennes - CNRS, Rennes, France
This perspective offers a viewpoint on how the challenges of molecular scattering investigations of astrophysical interest have evolved in recent years. Computational progress has steadily expanded collisional databases and provided essential tools for modeling non-LTE astronomical regions. However, the observational leap enabled by the JWST and new observational facilities has revealed critical gaps in these databases. In this framework, two major frontiers emerge: the characterization of collisional processes involving heavy projectiles, and the treatment of ro-vibrational excitation. The significant computational effort of these investigations emphasizes the need to test and develop robust theoretical methods and approximations, capable of extending the census of collisional coefficients required for reliable astrophysical modeling. Recent developments in these directions are outlined, with particular attention to their application and their potential to broaden the coverage of molecular systems and physical environments.
1 Introduction
The past decade has witnessed major progress in collisional excitation studies for astrophysical applications. These advances have been decisive for interpreting astronomical observations and constraining the physical conditions of interstellar and circumstellar environments, where molecular level populations often deviate from local thermodynamic equilibrium (LTE). In non-LTE regimes, radiative and collisional processes contribute on comparable timescales to molecular (de)-excitations. Consequently, the fundamental molecular data needed to interpret observational spectra are: energy levels, radiative rates and collisional rate coefficients. While spectroscopic measurements provide access to the first two, the determination of collisional rate coefficients largely relies on accurate quantum calculations (Roueff and Lique, 2013; Lique and Faure, 2019; Tonolo and Alessandrini, 2024).
So far, state-of-the-art computational strategies, based on both an accurate treatment of the electronic motion (e.g., by using the gold-standard CCSD(T) method, as shown in Faure (2022) and references therein) and the close-coupling (CC) time-independent quantum formalism (Arthurs and Dalgarno, 1960) to solve the nuclear problem, have been the primary tool for producing complete datasets of collisional rate coefficients. For diatomic and triatomic species, typical accuracies are within 10%–20% for collisional rate coefficients (Lique et al., 2010; Yang et al., 2010), and 1%–10% for pressure broadening coefficients (Tonolo et al., 2021; Tonolo et al., 2025a; Bizzocchi et al., 2024). In parallel, improved experimental techniques, based on molecular beams, flow-based methods and laser spectroscopy, have begun to provide very detailed information on collisions, including the observation of quantum resonances and interference effects (Chefdeville et al., 2013; Brouard et al., 2014; Bergeat et al., 2015; de Jongh et al., 2020; Toscano et al., 2020; Labiad et al., 2022). Experimental setups cannot yet probe collision dynamics across the full molecular diversity and physical conditions of astrophysical media, but they play a crucial role in testing and validating theoretical methods and approximations.
Nowadays, computed data are collected in collisional databases that are in constant growth, e.g., BASECOL (Dubernet et al., 2024), EMAA (Faure et al., 2025) and LAMDA (van der Tak et al., 2020). These databases now cover a large number of molecules of astrochemical interest, mostly small species (less than five atoms), including radicals and ions, interacting with the main projectiles of the interstellar medium (ISM): H2, He and H. In most cases, rate coefficients are resolved for both fine and hyperfine structure, when present, and also include the most relevant isotopologues (Faure and Lique, 2012; Denis-Alpizar et al., 2015; Tonolo et al., 2022).
The field has made significant progress in this direction, and further developments are underway, with new datasets covering a broader range of molecules and temperature regimes. For example, collisional studies are increasingly tackling the characterization of complex organic molecules (COMs; Faure et al. (2011); Faure et al. (2019); Mandal et al. (2022); Ben Khalifa et al. (2022); Ben Khalifa et al. (2023); Ben Khalifa et al. (2024); Ben Khalifa and Loreau (2024); Dagdigian (2024b); Dagdigian (2024a); Demes et al. (2024); Bop and Lique (2025)), defined as species with more than five atoms and at least one carbon (Herbst and Van Dishoeck, 2009). COMs have been detected in numerous interstellar observations, where they play a key role in astrochemical networks (McGuire, 2022). Yet, their large size often makes the use of full quantum CC methods computationally prohibitive. Exact CC calculations are extremely burdensome also when addressing the hot regions of the ISM, such as hot cores or protoplanetary nebulae, where the high temperatures (often exceeding 100 K) demand the extension of scattering calculations to a broader kinetic energy range (Dumouchel et al., 2010; Faure et al., 2016; Tonolo et al., 2024). In such cases, viable strategies involve solving the nuclear Schrödinger equation with approximate quantum methods, such as coupled states (CS; McGuire and Kouri (1974)) or infinite order sudden (IOS; Pack (1974)) approximations. In the former one, off-diagonal Coriolis couplings are neglected in the scattering Hamiltonian, which often preserves good accuracy while reducing the computational cost by a factor of 3–10 compared to CC (Toboła et al., 2007; Lique and Kłos, 2008; Troscompt et al., 2009). The latter, based on the assumption that the time between collisions is much shorter than the rotational time, decouples different orientations of the collider. This works well at high collisional energies but may lead to physically unreliable results at low energies, where molecular rotation strongly affects cross sections. The mixed quantum/classical theory (MQCT) offers also a promising compromise in this direction, being able to extend scattering calculations to previously inaccessible systems and temperatures (e.g., Loreau et al. (2018a)). Developed by Semenov et al. (2020) and Mandal et al. (2024), MQCT combines a quantum treatment of internal ro-vibrational motion with a classical description of scattering, achieving a good balance between accuracy and efficiency. At temperatures above 100 K, MQCT results are typically within a factor of 2 with respect to CC calculations (Babikov and Semenov, 2016; Joy et al., 2024).
At high temperatures, classical treatments of the nuclear motion, as in the quasi-classical trajectory (QCT) method, are also worth to mention as valid alternatives, noticeably reducing the computational effort while providing good accuracies (e.g., Faure et al. (2006); Loreau et al. (2018a)). Despite major progress in methodology and the steady expansion of collisional databases, the challenges ahead continue to intensify. These are mostly driven by the rapid growth of observational data. Breakthroughs from modern astronomical facilities, such as the ALMA array of radiotelescopes (Wootten and Thompson, 2009), the James Webb Space Telescope (JWST; Gardner et al. (2023)), and the SKA precursors and pathfinders (Röttgering, 2003; Tingay et al., 2016; Jonas and Team, 2016), have significantly broadened the horizons of astrochemistry. Their unprecedented sensitivity and spectral resolution are opening new windows onto diverse environments, including planetary atmospheres, cometary comae, and exoplanets (de Wit et al., 2024; Cordiner et al., 2024; Nixon et al., 2025). Despite steep vertical gradients in molecular densities often drive strong departures from LTE in such regions, retrieving collisional datasets to support astrochemical models remains challenging, costly, and far from straightforward. For instance, the presence of heavy colliders such as N2, CO, CO2 and H2O requires the development and application of advanced computational strategies. At the same time, infrared observations of vibrational molecular signatures, boosted by the MIRI (Wright et al., 2004) and NIRSPEC (Bagnasco et al., 2007) instruments on JWST, are flourishing, providing unprecedented insights into the underlying chemistry. Accurately modeling collisional processes under these conditions remains a pressing frontier, driving ongoing innovation in theoretical chemistry and molecular physics.
In the following, I will focus on these emerging frontiers. From my perspective, these research areas will play a crucial role in keeping pace the rapid observational advances brought by the new generation of astronomical instruments and by in situ space missions. In §2, current investigations of molecular de-excitation induced by collisions with heavy partners (i.e., species heavier than H2) are presented, while §3 discusses the methodologies of particular relevance for treating ro-vibrational excitation. § 4 concludes with a summary and outlook for future developments.
2 Heavy colliders
Most of collisional investigations of astrophysical interest address (de-)excitation processes induced by H2 and He, the most abundant projectiles in the ISM. Yet, recent observational advances are revealing environments with far greater chemical diversity.
A representative example is cometary comae, the gaseous envelopes that sublimate from cometary ices under solar radiation (Bockelée-Morvan, 2008; Roth et al., 2021; Biver et al., 2022; Cordiner et al., 2023). The composition of cometary comae carries the chemical legacy of the early stages of Solar System formation, preserved in cometary ices and released through sublimation, and provides clues on the potential delivery of prebiotic molecules to Earth (Matthews and Minard, 2008; Mumma and Charnley, 2011; Jung and Choe, 2013). However, the low densities of cometary comae (1
Titan’s atmosphere provides another illustrative case. Titan is the only other body in the Solar System, besides Earth, with a dense, N2-rich atmosphere and features reminiscent of primordial Earth. Here, strong vertical abundance gradients, especially above 800 km in the thermosphere, produce pronounced non-LTE effects (Rezac et al., 2013; Nixon et al., 2025). Similar conditions are found in the water vapor dominated atmospheres of Jupiter’s Moons Ganymede, Calisto, and Europa, where non-LTE effects peak at sub-solar points due to intense sublimation and photo-desorption processes (Mogan et al., 2021; Enya et al., 2022; Vorburger et al., 2022). To conclude, non-LTE effects are also well documented in the CO2 rich atmospheres of Mars (Johnson et al., 1976; Piccialli et al., 2016) and Venus (López-Valverde et al., 2007; Gilli et al., 2009).
These example underscore the critical role of collisional rate coefficients in modeling chemically diverse environments. The presence of heavy colliders, however, introduces substantial challenges for scattering calculations, both methodological and computational. Indeed, the dense rotational structure of N2, CO, CO2 and H2O multiplies the number of collisional channels to be considered, making full quantum scattering calculations unfeasible in most cases.
Recently, the Statistical Adiabatic Channel Model (SACM), originally introduced by Quack and Troe (1975) and later refined by Loreau et al. (2018b), showed particular promise for very low-temperature environments such as cometary atmospheres. While drastically reducing the computational cost, the SACM is particularly accurate for systems that form a stable intermediate complex, allowing for a statistical energy redistribution. This makes it especially effective for collisions among molecules forming stable complexes, such as in ionic interactions or collisions between strongly polar species (Loreau et al., 2018b; Loreau et al., 2018a; Balança et al., 2020; Pirlot Jankowiak and Lique, 2025). For cometary applications, the SACM has already been tested on several systems, typically deviating by less than a factor of 2 from exact CC results for rate coefficients thermalized with respect to the rotational temperature of the projectile (Godard Palluet et al., 2025; Tonolo et al., 2025b). For weakly bound systems such as CO
Despite recent progress, collisional datasets involving heavy colliders remain scarce. Table 1 summarizes the few available cases of astrophysical interest involving pure rotational transitions, together with the methods employed and their ranges of applicability.
Table 1. State-of-the-art datasets of collisional rate coefficients relevant for modeling cometary comae, with corresponding references.
Faced with this paucity of data, a common workaround is to use existing datasets for the same molecular target to approximate its behavior with missing colliders. To test this assumption, Figure 1 compares a reduced set of collisional rate coefficients for the rotational de-excitation of CO (Faure et al., 2020; Żółtowski et al., 2022; Dagdigian, 2022), HCN (Dumouchel et al., 2010; Hernández Vera et al., 2017; Tonolo et al., 2025b; Żółtowski et al., 2025), and CS (Denis-Alpizar et al. (2018); Godard Palluet et al. (2025); Godard et al., in prep.), starting from
Figure 1. Comparison of a reduced set of rate coefficients (cm3 s-1) for the de-excitation starting from the
3 Ro-vibrational excitation
The advent of JWST, together with the high resolution of new generation of observational facilities, have lifted the veil on ro-vibrational spectroscopy as a diagnostic tool of scarcely explored astrophysical environments, ranging from warm shocked gas and interstellar hot cores to planetary and exoplanetary atmospheres (Ahrer and Alderson, 2023; Espinoza and Perrin, 2025; van Dishoeck et al., 2025). In these regions, vibrationally excited states are significantly populated. Ro-vibrational spectra also reveal information inaccessible to purely rotational diagnostics: molecules without permanent dipole moments, such as CH4, C2H2, and CO2, become observable when vibrational excitation breaks their intrinsic symmetry (Lacy, 2013). However, non-LTE effects are particularly pronounced under these conditions (Kristensen et al., 2012; Fossati et al., 2021; Borsa et al., 2022; Wright et al., 2022; Bowesman et al., 2025), with deviations from thermal equilibrium often exceeding those seen in purely rotational populations (see Bruderer et al. (2015); Van Gelder et al. (2024) for illustrative cases of HCN and SO2). Moreover, the large radiative de-excitation rates of ro-vibrational transitions substantially raise the critical densities required for vibrational thermalization. Consequently, assuming vibrational LTE at the gas kinetic temperature may lead to misinterpretations. Accurate datasets of collisional rate coefficients are therefore essential for reliable radiative transfer models of these environments.
In the past, vibrational and ro-vibrational collisional investigations were conducted mainly relying on QCT (Aoiz et al., 1992; Varandas and Marques, 1994), and quantum-classical (QC, or semiclassical; Billing (1984); Billing (1987)) methods. While the former one uniquely relies on classical dynamics treatments, the latter lays the same theoretical foundations of MQCT, and describes molecular rotations and translational motion in a classical way, while introducing a quantum description of the vibrational degrees of freedom. QC methods have undergone significant refinements in recent years (Hong et al., 2023a; Yang et al., 2025) and are now widely employed to expand collisional databases, typically covering very high temperatures (up to
However, the lack of a proper quantum treatment remains a major limitation, preventing high accuracy below 200 K and thereby reducing the reliability of such data for most astrophysical applications. On the other hand, quantum investigations that fully account for ro-vibrational degrees of freedom have so far been limited to very small systems, typically involving only diatomic molecules (e.g., Alexander (1973); Schaefer and Lester Jr (1975); Ramaswamy and Rabitz (1977); Balakrishnan et al. (2000); Tao and Alexander (2007); Kłos et al. (2008); Stewart et al. (2010)). The vibrational modes that typically involve lower frequencies, and are therefore more easily populated (leading to stronger observational lines) are bending modes or large-amplitude modes such as the CH3 internal rotation (torsion mode). However, only a handful of full quantum datasets exists for molecules with more than two atoms, as summarized in Table 2. This limitation reflects the methodological and numerical challenges of computing collision-induced ro-vibrational excitation. Such calculations require higher dimensional treatment of the potential, large vibrational basis sets, and the evaluation of complex multidimensional integrals to obtain the scattering matrix.
Table 2. State-of-the-art datasets of collisional rate coefficients for polyatomic molecules, which include a quantum treatment of ro-vibrational excitation for selected vibrational modes, with corresponding references.
An efficient way out in this direction was proposed by Selim et al. (2021), who treated all rotational channels for each vibrational quantum number with the full CC method, while handling the weaker couplings between vibrational states perturbatively with the multi-channel distorted-wave Born approximation (MC-DWBA). This strategy reduces CPU time by a factor of 3 without compromising accuracy. Nevertheless, such gain remains insufficient to address larger systems and broader energy ranges. To further reduce the computational effort, the same authors benchmarked the CS approximation against CC results, with also two improved variants that include Coriolis couplings to first order, i.e., the nearest-neighbor Coriolis coupling approximation (NNCC; Yang et al. (2018); Selim et al. (2022)). For the CO2–He system, NNCC surpassed standard CS in reproducing CC results. In terms of CPU and memory requirements, NNCC offered best balance between efficiency and accuracy for both inelastic cross sections and rate coefficients. Moreover, combining MC-DWBA with NNCC yielded similar improvements in computational efficiency as with CC, without loss of accuracy.
More recently, the same authors tested the VCC-IOS approximation for state-to-state ro-vibrational transitions of CO2 colliding with He (Selim et al., 2023). Originally developed by Clary and co-workers in the 1980s (Clary, 1981; Clary, 1982; Clary et al., 1995; Banks and Clary, 1987; Wickham-Jones et al., 1987), VCC-IOS combines a CC treatment of vibrational motion with the IOS approximation for rotations, drastically reducing the computational cost. This method has long proven effective for vibrational quenching and ro-vibrational (de)-excitation in diatomic systems (Lique et al., 2006; Lique and Spielfiedel, 2007; Toboła et al., 2008; Balança and Dayou, 2017), but its applicability to polyatomic molecules was partially explored. The results showed a strong dependence on vibrational frequency: for high frequency modes (symmetric and asymmetric CO2 stretching), VCC-IOS deviated from CC by up to three orders of magnitude (Selim et al., 2021). In contrast, for the low-frequency bending mode of CO2, the method reproduced collisional coefficients within
When addressing bending modes of triatomic molecules, another promising strategy was proposed by Denis-Alpizar et al. (2013): the rigid-bender averaged approximation (RBAA). Here, the interaction potential is averaged over the bending wave function before scattering calculations, effectively reducing the problem to an atom colliding with a linear molecule whose rotation and bending motions are decoupled. Although drastic, this approximation shows promise for extending ro-vibrational collisional studies to medium- and large-sized polyatomic systems (Stoecklin et al., 2013).
Finally, it is worth mentioning the significant progress achieved over the years in predicting the vibrational excitation of polyatomic molecules by electron impact. A paradigmatic case addresses the H2O molecule, which has long served as a benchmark system for testing and validating various theoretical approaches (Nishimura and Itikawa, 1995; Curik and Cársky, 2003; Nishimura and Gianturco, 2004; Song et al., 2021). Building upon these studies, Faure and Josselin (2008) derived for the first time ro-vibrational rate coefficients under the assumption of a complete decoupling between rotational and vibrational motions. More recently, Ayouz et al. (2021) end Ayouz et al. (2024) have developed and refined an ab initio methodology capable of reproducing vibrational thermalized rate coefficients with remarkable accuracy over a broad temperature range (10–10000 K), encompassing the 13 lowest energy levels of H2O. The extension of these datasets to rotationally resolved vibrational rate coefficients is currently in progress.
4 Discussion
The recent advances in computational methods have considerably expanded collisional databases, enabling progress on several long-standing challenges. Yet, this is only the tip of the iceberg. The breakthroughs delivered by the JWST have raised the stakes, providing new observational data from complex environments such as cometary comae, planetary and exoplanetary atmospheres, and warm shocked regions. In all these regions, strong departures from LTE are frequently observed, highlighting the need for accurate collisional rate coefficients to support radiative transfer models.
In this perspective, two major frontiers have been identified and discussed. The first concerns collisions involving heavy colliders. Here, the SACM approach appears promising to address systems forming stable intermediates at low temperatures. The CS approximation is more suitable for weakly bound systems, while MQCT methods provide an effective strategy to extend calculations to higher temperatures. The second frontier involves the treatment of ro-vibrational excitation. Hybrid strategies, such as combining CC with perturbative schemes or employing improved variants of the CS approximation, have shown encouraging results. Together, these developments outline a toolkit of methods that, if carefully benchmarked, can help address these challenges.
Still, there is room for improvement. The systems studied so far are few, and methodological benchmarks remain fragmented or incomplete. Even when new methods show promise on a given target, their general applicability remains untested.
Expanding collisional databases is therefore an urgent priority. This will require coordinated efforts on multiple fronts: developing and testing approximate quantum approaches, benchmarking them systematically against full quantum results, and producing datasets covering the relevant physical conditions of planetary, cometary, and exoplanetary environments. Machine learning may also play a pivotal role in this regard, offering efficient ways to interpolate and extrapolate collisional data, reduce computational cost, and uncover transferable patterns across molecular systems (the reader is referred to Mihalik et al. (2025) and reference therein for some illustrative examples). Data-driven models trained on accurate quantum calculations could accelerate the expansion of collisional databases, extending them to larger systems and broader physical regimes.
This perspective is not intended as an exhaustive review of past work. Rather, its goal is to emphasize the evolving challenges in the field and to suggest possible directions for addressing them in the coming years.
Data availability statement
The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.
Author contributions
FT: Project administration, Validation, Conceptualization, Methodology, Data curation, Formal Analysis, Visualization, Writing – review and editing, Investigation, Funding acquisition, Supervision, Writing – original draft, Resources, Software.
Funding
The author(s) declare that no financial support was received for the research and/or publication of this article.
Acknowledgments
AcknowledgementsI would like to acknowledge Prof. François Lique and Dr. Paul Pirlot Jankowiak for the fruitful discussions and the careful reading and insightful comments for this manuscript. Moreover, I acknowledge the “Programme National de Planétologie” (PNP) under the responsibilityof INSU, CNRS (France) for financial support.
Conflict of interest
The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declare that no Generative AI was used in the creation of this manuscript.
Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
Ahrer, E., and Alderson, L. (2023). JWST transiting exoplanet community early release science team. Nature 614, 649. doi:10.1038/s41586-022-05269-w
Alexander, M. H. (1973). Fully quantum study of near resonant D2-D2vibrational energy transfer. J. Chem. Phys. 59, 6254–6265. doi:10.1063/1.1680003
Aoiz, F. J., Herrero, V. J., and Sáez Rábanos, V. (1992). Quasiclassical state to state reaction cross sections for D + H2 (v=0, j= 0) → HD (v’, j’) + H. Formation and characteristics of short-lived collision complexes. J. Chem. Phys. 97, 7423–7436. doi:10.1063/1.463514
Arthurs, A., and Dalgarno, A. (1960). The theory of scattering by a rigid rotator. Proc. R. Soc. Lond 256, 540–551. doi:10.1098/rspa.1960.0125
Ayouz, M., Faure, A., Tennyson, J., Tudorovskaya, M., and Kokoouline, V. (2021). Cross sections and rate coefficients for vibrational excitation of H2O by electron impact. Atoms 9, 62. doi:10.3390/atoms9030062
Ayouz, M., Faure, A., and Kokoouline, V. (2024). Theoretical study of the electron-induced vibrational excitation of H2O. Astronomy Astrophysics 687, A3. doi:10.1051/0004-6361/202449361
Babikov, D., and Semenov, A. (2016). Recent advances in development and applications of the mixed quantum/classical theory for inelastic scattering. J. Phys. Chem. A 120, 319–331. doi:10.1021/acs.jpca.5b09569
Bagnasco, G., Kolm, M., Ferruit, P., Honnen, K., Koehler, J., Lemke, R., et al. (2007). Overview of the near-infrared spectrograph (NIRSpec) instrument on-board the James Webb Space Telescope (JWST). Cryog. Opt. Syst. Instrum. 6692, 174–187. doi:10.1117/12.735602
Balakrishnan, N., Dalgarno, A., and Forrey, R. (2000). Vibrational relaxation of co by collisions with 11He at ultracold temperatures. J. Chem. Phys. 113, 621–627. doi:10.1063/1.481838
Balança, C., and Dayou, F. (2017). Ro-vibrational excitation of SiO by collision with helium at high temperature. Mon. Notices R. Astronomical Soc. 469, 1673–1681. doi:10.1093/mnras/stx925
Balança, C., Scribano, Y., Loreau, J., Lique, F., and Feautrier, N. (2020). Inelastic rate coefficients for collisions of N2H+ with H2. Mon. Notices R. Astronomical Soc. 495, 2524–2530. doi:10.1093/mnras/staa1384
Banks, A., and Clary, D. (1987). Coupled states calculations on vibrational relaxation in He + CO2 (0110) and He + CO. J. Chem. Phys. 86, 802–812. doi:10.1063/1.452282
Ben Khalifa, M., and Loreau, J. (2024). Rotational excitation of interstellar benzonitrile by helium atoms. Mon. Notices R. Astronomical Soc. 527, 846–854. doi:10.1093/mnras/stad3201
Ben Khalifa, M., Dagdigian, P. J., and Loreau, J. (2022). Interaction of CH3CN and CH3NC with He: potential energy surfaces and low-energy scattering. J. Phys. Chem. A 126, 9658–9666. doi:10.1021/acs.jpca.2c06925
Ben Khalifa, M., Dagdigian, P., and Loreau, J. (2023). Collisional excitation of methyl (iso) cyanide by He atoms: rate coefficients and isomerism effects. Mon. Notices R. Astronomical Soc. 523, 2577–2586. doi:10.1093/mnras/stad1508
Ben Khalifa, M., Darna, B., and Loreau, J. (2024). Collisional excitation of propyne (CH3CCH) by He atoms. Astronomy Astrophysics 683, A53. doi:10.1051/0004-6361/202348717
Bergeat, A., Onvlee, J., Naulin, C., Van Der Avoird, A., and Costes, M. (2015). Quantum dynamical resonances in low-energy CO (j = 0)+ He inelastic collisions. Nat. Chem. 7, 349–353. doi:10.1038/nchem.2204
Billing, G. D. (1984). Semiclassical treatment of molecular roto-vibrational energy transfer. Comput. Phys. Rep. 1, 239–296. doi:10.1016/0167-7977(84)90006-6
Billing, G. (1987). Rate constants for vibrational transitions in diatom-diatom collisions. Comput. Phys. Commun. 44, 121–136. doi:10.1016/0010-4655(87)90022-1
Billing, G., Coletti, C., Kurnosov, A., and Napartovich, A. (2003). Sensitivity of molecular vibrational dynamics to energy exchange rate constants. J. Phys. B Atomic, Mol. Opt. Phys. 36, 1175–1192. doi:10.1088/0953-4075/36/6/308
Biver, N., Bockelée-Morvan, D., Crovisier, J., Davies, J., Matthews, H., Wink, J., et al. (1999). Spectroscopic monitoring of comet C/1996 B2 (Hyakutake) with theJCMT and IRAM radio telescopes. Astronomical J. 118, 1850–1872. doi:10.1086/301033
Biver, N., Boissier, J., Bockelée-Morvan, D., Crovisier, J., Cottin, H., Cordiner, M., et al. (2022). Observations of comet c/2020 f3 (neowise) with iram telescopes. Astronomy Astrophysics 668, A171. doi:10.1051/0004-6361/202244970
Bizzocchi, L., Tonolo, F., Giuliano, B. M., Caselli, P., Melosso, M., Dore, L., et al. (2024). Millimeter to THz spectroscopy of HC18O+ and HC17O+: accurate rest frequencies for astrophysical studies. Astrophysical J. 970, 26. doi:10.3847/1538-4357/ad5007
Bockelée-Morvan, D. (2008). Cometary science with alma. Astrophysics Space Sci. 313, 183–189. doi:10.1007/s10509-007-9641-2
Bop, C. T., and Lique, F. (2025). Guidelines for non-LTE modelling of cyanopolyynes. Astronomy Astrophysics 695, A132. doi:10.1051/0004-6361/202553698
Borsa, F., Fossati, L., Koskinen, T., Young, M. E., and Shulyak, D. (2022). High-resolution detection of neutral oxygen and non-LTE effects in the atmosphere of KELT-9b. Nat. Astron. 6, 226–231. doi:10.1038/s41550-021-01544-4
Bostan, D., Mandal, B., Joy, C., Żółtowski, M., Lique, F., Loreau, J., et al. (2024). Mixed quantum/classical calculations of rotationally inelastic scattering in the CO + CO system: a comparison with fully quantum results. Phys. Chem. Chem. Phys. 26, 6627–6637. doi:10.1039/d3cp05369e
Boursier, C., Mandal, B., Babikov, D., and Dubernet, M. (2020). New H2O–H2O collisional rate coefficients for cometary applications. Mon. Notices R. Astronomical Soc. 498, 5489–5497. doi:10.1093/mnras/staa2713
Bowesman, C. A., Yurchenko, S. N., Al-Refaie, A., and Tennyson, J. (2025). TIRAMISU: Non-LTE radiative transfer for molecules in exoplanet atmospheres. arXiv preprint arXiv:2508.12873. doi:10.48550/arXiv.2508.12873
Brouard, M., Parker, D. H., and van de Meerakker, S. Y. (2014). Taming molecular collisions using electric and magnetic fields. Chem. Soc. Rev. 43, 7279–7294. doi:10.1039/c4cs00150h
Bruderer, S., Harsono, D., and Van Dishoeck, E. F. (2015). Ro-vibrational excitation of an organic molecule (HCN) in protoplanetary disks. Astronomy Astrophysics 575, A94. doi:10.1051/0004-6361/201425009
Buffa, G., Tarrini, O., Scappini, F., and Cecchi-Pestellini, C. (2000). H2O–H2O collision rate coefficients. Astrophysical J. Suppl. Ser. 128, 597–601. doi:10.1086/313389
Chefdeville, S., Kalugina, Y., van de Meerakker, S. Y., Naulin, C., Lique, F., and Costes, M. (2013). Observation of partial wave resonances in low-energy O2–H2 inelastic collisions. Science 341, 1094–1096. doi:10.1126/science.1241395
Clary, D. (1981). Quantum study of vibrational excitation in the three-dimensional collisions of CO2 with rare gas atoms. J. Chem. Phys. 75, 209–219. doi:10.1063/1.441827
Clary, D. (1982). Ab initio computation of vibrational relaxation rate coefficients for the collisions of CO2 with helium and neon atoms. Chem. Phys. 65, 247–257. doi:10.1016/0301-0104(82)85073-8
Clary, D. C., Gilbert, R. G., Bernshtein, V., and Oref, I. (1995). Mechanisms for supercollisions. Faraday Discuss. 102, 423–433. doi:10.1039/fd9950200423
Cordiner, M. A., Coulson, I., Garcia-Berrios, E., Qi, C., Lique, F., Zołtowski, M., et al. (2022). A SUBLIME 3D model for cometary coma emission: the hypervolatile-rich comet C/2016 R2 (PanSTARRS). Astrophysical J. 929, 38. doi:10.3847/1538-4357/ac5893
Cordiner, M., Roth, N., Milam, S., Villanueva, G., Bockelée-Morvan, D., Remijan, A., et al. (2023). Gas sources from the coma and nucleus of comet 46P/Wirtanen observed using ALMA. Astrophysical J. 953, 59. doi:10.3847/1538-4357/ace0bc
Cordiner, M., Thelen, A., Cavalie, T., Cosentino, R., Fletcher, L. N., Gurwell, M., et al. (2024). Atacama large aperture submillimeter telescope (AtLAST) science: planetary and cometary atmospheres. Open Res. Eur. 4, 78. doi:10.12688/openreseurope.17473.2
Curik, R., and Cársky, P. (2003). Vibrationally inelastic electron scattering on polyatomic molecules by the discretemomentum representation (DMR) method. J. Phys. B 36, 2165–2177. doi:10.1088/0953-4075/36/11/303
Dagdigian, P. J. (2013). Theoretical investigation of collisional energy transfer in polyatomic intermediates. Int. Rev. Phys. Chem. 32, 229–265. doi:10.1080/0144235x.2012.758543
Dagdigian, P. J. (2022). Collisional excitation of isotopologues of carbon monoxide by molecular hydrogen. Mon. Notices R. Astronomical Soc. 514, 2214–2219. doi:10.1093/mnras/stac1430
Dagdigian, P. J. (2024a). Rotational excitation of methanol in collisions with molecular hydrogen. Mon. Notices R. Astronomical Soc. 527, 2209–2213. doi:10.1093/mnras/stad3303
Dagdigian, P. J. (2024b). Rotational excitation of methyl mercaptan (CH3SH) in collisions with molecular hydrogen. Mon. Notices R. Astronomical Soc. 535, 247–253. doi:10.1093/mnras/stae2195
Dagdigian, P. J., and Alexander, M. H. (2011). Theoretical investigation of rotationally inelastic collisions of the methyl radical with helium. J. Chem. Phys. 135, 064306. doi:10.1063/1.3624525
de Jongh, T., Besemer, M., Shuai, Q., Karman, T., van der Avoird, A., Groenenboom, G. C., et al. (2020). Imaging the onset of the resonance regime in low-energy NO-He collisions. Science 368, 626–630. doi:10.1126/science.aba3990
de Wit, J., Doyon, R., Rackham, B. V., Lim, O., Ducrot, E., Kreidberg, L., et al. (2024). A roadmap for the atmospheric characterization of terrestrial exoplanets with JWST. Nat. Astron. 8, 810–818. doi:10.1038/s41550-024-02298-5
Demes, S., Bop, C. T., Khalifa, M. B., and Lique, F. (2024). First close-coupling study of the excitation of a large cyclic molecule: collision of cC5H6 with He. Phys. Chem. Chem. Phys. 26, 16829–16837. doi:10.1039/d4cp01380h
Denis-Alpizar, O., Stoecklin, T., Halvick, P., and Dubernet, M.-L. (2013). The interaction of He with vibrating HCN: potential energy surface, bound states, and rotationally inelastic cross sections. J. Chem. Phys. 139, 034304. doi:10.1063/1.4813125
Denis-Alpizar, O., Stoecklin, T., and Halvick, P. (2014). Rovibrational energy transfer in the He-C3 collision: potential energy surface and bound states. J. Chem. Phys. 140, 084316. doi:10.1063/1.4866839
Denis-Alpizar, O., Stoecklin, T., and Halvick, P. (2015). Isotopic effects in the collision of HCN with He: substitution of HCN by DCN. Mon. Notices R. Astronomical Soc. 453, 1317–1323. doi:10.1093/mnras/stv1748
Denis-Alpizar, O., Stoecklin, T., Guilloteau, S., and Dutrey, A. (2018). New ratecoefficients of CS in collision with para- and ortho-H2 and astrophysical implications. Mon. Notices R. Astronomical Soc. 478, 1811–1817. doi:10.1093/mnras/sty1177
Dubernet, M.-L., and Quintas-Sánchez, E. (2019). First quantum study of the rotational excitation of HCN by para-H2O: convergence of quantum results, influence of the potential energy surface, and approximate rate coefficients of interest for cometary atmospheres. Mol. Astrophys. 16, 100046. doi:10.1016/j.molap.2019.100046
Dubernet, M.-L., Boursier, C., Denis-Alpizar, O., Ba, Y. A., Moreau, N., Zwölf, C. M., et al. (2024). BASECOL2023 scientific content. Astronomy Astrophysics 683, A40. doi:10.1051/0004-6361/202348233
Dumouchel, F., Faure, A., and Lique, F. (2010). The rotational excitation of HCN and HNC by He: temperature dependence of the collisional rate coefficients. Mon. Notices R. Astronomical Soc. 406, 2488–2492. doi:10.1111/j.1365-2966.2010.16826.x
Enya, K., Kobayashi, M., Kimura, J., Araki, H., Namiki, N., Noda, H., et al. (2022). The Ganymede Laser Altimeter (GALA) for the Jupiter icy moons explorer (JUICE): mission, science, and instrumentation of its receiver modules. Adv. space Res. 69, 2283–2304. doi:10.1016/j.asr.2021.11.036
Espinoza, N., and Perrin, M. D. (2025). Highlights from exoplanet observations by the James webb space telescope. arXiv preprint arXiv:2505.20520. doi:10.48550/arXiv.2505.20520
Faure, A. (2022). Collisional rate coefficients for astrophysics. Proc. Int. Astronomical Union 18, 123–132. doi:10.1017/s1743921323000029
Faure, A., and Josselin, E. (2008). Collisional excitation of water in warm astrophysical media-I. Rate coefficients for rovibrationally excited states. Astronomy Astrophysics 492, 257–264. doi:10.1051/0004-6361:200810717
Faure, A., and Lique, F. (2012). The impact of collisional rate coefficients on molecular hyperfine selective excitation. Mon. Notices R. Astronomical Soc. 425, 740–748. doi:10.1111/j.1365-2966.2012.21601.x
Faure, A., Valiron, P., Wernli, M., Wiesenfeld, L., Rist, C., Noga, J., et al. (2005a). A full nine-dimensional potential-energy surface for hydrogen molecule-water collisions. J. Chem. Phys. 122, 221102. doi:10.1063/1.1935515
Faure, A., Wiesenfeld, L., Wernli, M., and Valiron, P. (2005b). The role of rotation in the vibrational relaxation of water by hydrogen molecules. J. Chem. Phys. 123, 104309. doi:10.1063/1.2033767
Faure, A., Wiesenfeld, L., Wernli, M., and Valiron, P. (2006). Rotational excitation of water by hydrogen molecules: comparison of results from classical and quantum mechanics. J. Chem. Phys. 124, 214310. doi:10.1063/1.2204032
Faure, A., Szalewicz, K., and Wiesenfeld, L. (2011). Potential energy surface and rotational cross sections for methyl formate colliding with helium. J. Chem. Phys. 135, 024301. doi:10.1063/1.3607966
Faure, A., Lique, F., and Wiesenfeld, L. (2016). Collisional excitation of HC3N by para-and ortho-H2. Mon. Notices R. Astronomical Soc. 460, 2103–2109. doi:10.1093/mnras/stw1156
Faure, A., Dagdigian, P. J., Rist, C., Dawes, R., Quintas-Sánchez, E., Lique, F., et al. (2019). Interaction of chiral propylene oxide (CH3CHCH2O) with helium: potential energy surface and scattering calculations. ACS Earth Space Chem. 3, 964–972. doi:10.1021/acsearthspacechem.9b00069
Faure, A., Lique, F., and Loreau, J. (2020). The effect of CO-H2O collisions in the rotational excitation of cometary CO. Mon. Notices R. Astronomical Soc. 493, 776–782. doi:10.1093/mnras/staa242
Faure, A., Bacmann, A., and Jacquot, R. (2025). Excitation of molecules and atoms for astrophysics (EMAA): a spectroscopic and collisional database. A&A 700, A266. doi:10.1051/0004-6361/202554403
Fossati, L., Young, M., Shulyak, D., Koskinen, T., Huang, C., Cubillos, P., et al. (2021). Non-local thermodynamic equilibrium effects determine the upper atmospheric temperature structure of the ultra-hot Jupiter KELT-9b. Astronomy Astrophysics 653, A52. doi:10.1051/0004-6361/202140813
García-Vázquez, R. M., Faure, A., and Stoecklin, T. (2024). Bending relaxation of H2O by collision with para-and Ortho-H2. ChemPhysChem 25, e202300698. doi:10.1002/cphc.202300698
Gardner, J. P., Mather, J. C., Abbott, R., Abell, J. S., Abernathy, M., Abney, F. E., et al. (2023). The james webb space telescope mission. PASP 135, 068001
Gilli, G., López-Valverde, M., Drossart, P., Piccioni, G., Erard, S., and Cardesín Moinelo, A. (2009). Limb observations of CO2 and CO non-LTE emissions in the Venus atmosphere by VIRTIS/Venus express. J. Geophys. Res. Planets 114. doi:10.1029/2008je003112
Godard Palluet, A., Dawes, R., Quintas-Sánchez, E., Batista-Planas, A., and Lique, F. (2025). A promising statistical approach for studying the collisional excitation induced by CO: application to the CS–CO system. J. Chem. Phys. 162, 241101. doi:10.1063/5.0273126
Green, S. (1993). Collisional excitation of CO by H2O - an astrophysicist’s guide to obtaining rate constants from coherent anti-stokes raman line shape data. Astrophysical J. 412, 436–440. doi:10.1086/172933
Herbst, E., and Van Dishoeck, E. F. (2009). Complex organic interstellar molecules. Annu. Rev. Astronomy Astrophysics 47, 427–480. doi:10.1146/annurev-astro-082708-101654
Hernández Vera, M., Lique, F., Dumouchel, F., Hily-Blant, P., and Faure, A. (2017). The rotational excitation of the HCN and HNC molecules by H2 revisited. Mon. Notices R. Astronomical Soc. 468, 1084–1091. doi:10.1093/mnras/stx422
Hong, Q., Sun, Q., Bartolomei, M., Pirani, F., and Coletti, C. (2020). Inelastic rate coefficients based on an improved potential energy surface for N2+N2 collisions in a wide temperature range. Phys. Chem. Chem. Phys. 22, 9375–9387. doi:10.1039/d0cp00364f
Hong, Q., Bartolomei, M., Coletti, C., Lombardi, A., Sun, Q., and Pirani, F. (2021a). Vibrational energy transfer in CO + N2 collisions: a database for V–V and V–T/R quantum-classical rate coefficients. Molecules 26, 7152. doi:10.3390/molecules26237152
Hong, Q., Sun, Q., Pirani, F., Valentín-Rodríguez, M. A., Hernández-Lamoneda, R., Coletti, C., et al. (2021b). Energy exchange rate coefficients from vibrational inelastic O2(Σg−3) + O2(Σg−3) collisions on a new spin-averaged potential energy surface. J. Chem. Phys. 154, 064304, doi:10.1063/5.0041244
Hong, Q., Storchi, L., Bartolomei, M., Pirani, F., Sun, Q., and Coletti, C. (2023a). Inelastic N2+H2 collisions and quantum-classical rate coefficients: large datasets and machine learning predictions. Eur. Phys. J. D 77, 128. doi:10.1140/epjd/s10053-023-00688-4
Hong, Q., Storchi, L., Sun, Q., Bartolomei, M., Pirani, F., and Coletti, C. (2023b). Improved quantum–classical treatment of N2–N2inelastic collisions: effect of the potentials and complete rate coefficient data sets. J. Chem. Theory Comput. 19, 8557–8571. doi:10.1021/acs.jctc.3c01103
Johnson, M., Betz, A., McLaren, R., Sutton, E., and Townes, C. (1976). Nonthermal 10 micron CO2 emission lines in the atmospheres of Mars and Venus. Astrophysical J. 208, L145–L148. doi:10.1086/182252
Jonas, J., and Team, M. (2016). The MeerKAT radio telescope. In: Proceedings of MeerKAT Science: On the Pathway to the SKA; 2016 May 25-27; Stellenbosch, South Africa.
Joy, C., Mandal, B., Bostan, D., Dubernet, M.-L., and Babikov, D. (2024). Mixed quantum/classical theory (MQCT) approach to the dynamics of molecule–molecule collisions in complex systems. Faraday Discuss. 251, 225–248. doi:10.1039/d3fd00166k
Jung, S. H., and Choe, J. C. (2013). Mechanisms of prebiotic adenine synthesis from HCN by oligomerization in the gas phase. Astrobiology 13, 465–475. doi:10.1089/ast.2013.0973
Kłos, J. A., Lique, F., Alexander, M. H., and Dagdigian, P. J. (2008). Theoretical determination of rate constants for vibrational relaxation and reaction of OH (XΠ2, v= 1) with O(P3) atoms. J. Chem. Phys. 129, 064306. doi:10.1063/1.2957901
Kristensen, L., van Dishoeck, E. F., Bergin, E., Visser, R., Yıldız, U., San Jose-Garcia, I., et al. (2012). Water in star-forming regions with Herschel (WISH)-II. Evolution of 557 GHz 110–101 emission in low-mass protostars. Astronomy Astrophysics 542, A8. doi:10.1051/0004-6361/201118146
Kurnosov, A., Napartovich, A., Shnyrev, S., and Cacciatore, M. (2010). A database for V–V state-to-state rate constants in N2–N2 and N2–CO collisions in a wide temperature range: dynamical calculations and analytical approximations. Plasma Sources Sci. Technol. 19, 045015. doi:10.1088/0963-0252/19/4/045015
Labiad, H., Fournier, M., Mertens, L. A., Faure, A., Carty, D., Stoecklin, T., et al. (2022). Absolute measurements of state-to-state rotational energy transfer between CO and H2 at interstellar temperatures. Phys. Rev. A 105, L020802. doi:10.1103/physreva.105.l020802
Lacy, J. H. (2013). Interpretation of infrared vibration-rotation spectra of interstellar and circumstellar molecules. Astrophysical J. 765, 130. doi:10.1088/0004-637x/765/2/130
Laskowski, M. R., Michael, T. J., Ogden, H. M., Alexander, M. H., and Mullin, A. S. (2022). Rotational energy transfer kinetics of optically centrifuged CO molecules investigated through transient IR spectroscopy and master equation simulations. Faraday Discuss. 238, 87–102. doi:10.1039/d2fd00068g
Lique, F., and Faure, A. (2019). Gas-phase chemistry in space: from elementary particles to complex organic molecules. Bristol: IOP Publishing Bristol.
Lique, F., and Kłos, J. (2008). Quantum scattering of SiS with H2: potential energy surface and rate coefficients at low temperature. J. Chem. Phys. 128, 034306. doi:10.1063/1.2820770
Lique, F., and Spielfiedel, A. (2007). Ro-vibrational excitation of CS by He. Astronomy Astrophysics 462, 1179–1185. doi:10.1051/0004-6361:20066422
Lique, F., Spielfiedel, A., Dhont, G., and Feautrier, N. (2006). Ro-vibrational excitation of the SO molecule by collision with the He atom. Astronomy Astrophysics 458, 331–337. doi:10.1051/0004-6361:20065713
Lique, F., Spielfiedel, A., Feautrier, N., Schneider, I. F., Kłos, J., and Alexander, M. H. (2010). Rotational excitation of CN (X Σ2+) by He: theory and comparison with experiments. J. Chem. Phys. 132, 024303. doi:10.1063/1.3285811
Lombardi, A., Pirani, F., Bartolomei, M., Coletti, C., and Laganà, A. (2019). Full dimensional potential energy function and calculation of state-specific properties of the CO + N2 inelastic processes within an open molecular science cloud perspective. Front. Chem. 7, 309. doi:10.3389/fchem.2019.00309
López-Valverde, M., Drossart, P., Carlson, R., Mehlman, R., and Roos-Serote, M. (2007). Non-LTE infrared observations at Venus: from NIMS/Galileo to VIRTIS/Venus express. Planet. Space Sci. 55, 1757–1771. doi:10.1016/j.pss.2007.01.008
Loreau, J., and Van der Avoird, A. (2015). Scattering of NH3 and ND3 with rare gas atoms at low collision energy. J. Chem. Phys. 143, 184303. doi:10.1063/1.4935259
Loreau, J., and van der Avoird, A. (2024). Vibrational energy transfer in ammonia–helium collisions. Faraday Discuss. 251, 249–261. doi:10.1039/d3fd00180f
Loreau, J., Faure, A., and Lique, F. (2018a). Scattering of CO with H2O: statistical and classical alternatives to close-coupling calculations. J. Chem. Phys. 148, 244308. doi:10.1063/1.5036819
Loreau, J., Lique, F., and Faure, A. (2018b). An efficient statistical method to compute molecular collisional rate coefficients. Astrophysical J. Lett. 853, L5. doi:10.3847/2041-8213/aaa5fe
Loreau, J., Faure, A., and Lique, F. (2022). The effect of water and electron collisions in the rotational excitation of HF in comets. Mon. Notices R. Astronomical Soc. 516, 5964–5971. doi:10.1093/mnras/stac2378
Ma, L., Alexander, M. H., and Dagdigian, P. J. (2011). Theoretical investigation of rotationally inelastic collisions of CH2 (ã) with helium. J. Chem. Phys. 134, 154307. doi:10.1063/1.3575200
Ma, L., Dagdigian, P. J., and Alexander, M. H. (2012). Theoretical investigation of rotationally inelastic collisions of CH2(X) with helium. J. Chem. Phys. 136, 224306, doi:10.1063/1.4729050
Ma, Q., Dagdigian, P. J., and Alexander, M. H. (2013). Theoretical study of the vibrational relaxation of the methyl radical in collisions with helium. J. Chem. Phys. 138, 104317. doi:10.1063/1.4794167
Ma, L., Dagdigian, P. J., and Alexander, M. H. (2014). Theoretical investigation of the relaxation of the bending mode of CH2(X3B1,ã1A1) by collisions with helium. J. Chem. Phys. 141, 214305, doi:10.1063/1.4902004
Mandal, B., and Babikov, D. (2023a). Improved temperature dependence of rate coefficients for rotational state-to-state transitions in H2O + H2O collisions. Astronomy Astrophysics 678, A51. doi:10.1051/0004-6361/202346895
Mandal, B., and Babikov, D. (2023b). Rate coefficients for rotational state-to-state transitions in H2O + H2O collisions for cometary and planetary applications, as predicted by mixed quantum-classical theory. Astronomy Astrophysics 671, A51. doi:10.1051/0004-6361/202245699
Mandal, B., Joy, C., Semenov, A., and Babikov, D. (2022). Mixed quantum/classical theory for collisional quenching of PAHs in the interstellar media. ACS Earth Space Chem. 6, 521–529. doi:10.1021/acsearthspacechem.1c00418
Mandal, B., Bostan, D., Joy, C., and Babikov, D. (2024). MQCT 2024: a program for calculations of inelastic scattering of two molecules (new version announcement). Comput. Phys. Commun. 294, 108938. doi:10.1016/j.cpc.2023.108938
Matthews, C. N., and Minard, R. D. (2008). Hydrogen cyanide polymers connect cosmochemistry and biochemistry. Proc. Int. Astronomical Union 4, 453–458. doi:10.1017/s1743921308022175
McGuire, B. A. (2022). 2021 census of interstellar, circumstellar, extragalactic, protoplanetary disk, and exoplanetary molecules. Astrophysical J. Suppl. Ser. 259, 30. doi:10.3847/1538-4365/ac2a48
McGuire, P., and Kouri, D. J. (1974). Quantum mechanical close coupling approach to molecular collisions. jz-conserving coupled states approximation. J. Chem. Phys. 60, 2488–2499. doi:10.1063/1.1681388
Mihalik, D. E., Wang, R., Yang, B., Stancil, P., Price, T., Forrey, R., et al. (2025). Accurate machine learning of rate coefficients for state-to-state transitions in molecular collisions. J. Chem. Phys. 162, 024116. doi:10.1063/5.0242182
Mogan, S. R. C., Tucker, O. J., Johnson, R. E., Vorburger, A., Galli, A., Marchand, B., et al. (2021). A tenuous, collisional atmosphere on callisto. Icarus 368, 114597. doi:10.1016/j.icarus.2021.114597
Mumma, M. J., and Charnley, S. B. (2011). The chemical composition of comets—emerging taxonomies and natal heritage. Annu. Rev. Astronomy Astrophysics 49, 471–524. doi:10.1146/annurev-astro-081309-130811
Ndengué, S. A., Dawes, R., and Gatti, F. (2015). Rotational excitations in CO–CO collisions at low temperature: time-independent and multiconfigurational time-dependent hartree calculations. J. Phys. Chem. A 119, 7712–7723. doi:10.1021/acs.jpca.5b01022
Nishimura, T., and Gianturco, F. A. (2004). Vibrational excitation of water by low-energy electron scattering: calculations and experiments. Europhys. Lett. 65, 179–185. doi:10.1209/epl/i2003-10077-3
Nishimura, T., and Itikawa, Y. (1995). Electron-impact vibrational excitation of water molecules. J. Phys. B Atomic, Mol. Opt. Phys. 28, 1995–2005. doi:10.1088/0953-4075/28/10/012
Nixon, C. A., Bézard, B., Cornet, T., Coy, B. P., de Pater, I., Es-Sayeh, M., et al. (2025). The atmosphere of Titan in late northern summer from JWST and keck observations. Nat. Astron., 1–13. doi:10.1038/s41550-025-02537-3
Pack, R. T. (1974). Space-fixed vs body-fixed axes in atom-diatomic molecule scattering. Sudden approximations. J. Chem. Phys. 60, 633–639. doi:10.1063/1.1681085
Phipps, S. P., Smith, T. C., Hager, G. D., Heaven, M. C., McIver, J., and Rudolph, W. (2002). Investigation of the state-to-state rotational relaxation rate constants for carbon monoxide (CO) using infrared double resonance. J. Chem. Phys. 116, 9281–9292. doi:10.1063/1.1472516
Piccialli, A., López-Valverde, M., Määttänen, A., González-Galindo, F., Audouard, J., Altieri, F., et al. (2016). CO2 non-LTE limb emissions in mars’ atmosphere as observed by OMEGA/mars express. J. Geophys. Res. Planets 121, 1066–1086. doi:10.1002/2015je004981
Pirlot Jankowiak, P., and Lique, F. (2025). Collisional energy transfer in the highly reactive OH+–H2 system. Phys. Rev. Lett. 134, 253002. doi:10.1103/hpcb-q7wh
Pottage, J., Flower, D., and Davis, S. L. (2003). The torsional excitation of methanol by helium. J. Phys. B Atomic, Mol. Opt. Phys. 37, 165–177. doi:10.1088/0953-4075/37/1/010
Quack, M., and Troe, J. (1975). Complex formation in reactive and inelastic scattering: statistical adiabatic channel model of unimolecular processes iii. Berichte Bunsenges. für Phys. Chem. 79, 170–183. doi:10.1002/bbpc.19750790211
Rabli, D., and Flower, D. (2011). Rotationally and torsionally inelastic scattering of methanol on helium. Mon. Notices R. Astronomical Soc. 411, 2093–2098. doi:10.1111/j.1365-2966.2010.17842.x
Ramaswamy, R., and Rabitz, H. (1977). Vibration–rotation relaxation in bimolecular collisions with application to para-hydrogen. J. Chem. Phys. 66, 152–159. doi:10.1063/1.433648
Rezac, L., Kutepov, A., Faure, A., Hartogh, P., and Feofilov, A. (2013). Rotational non-LTE in HCN in the thermosphere of Titan: implications for the radiative cooling. Astronomy Astrophysics 555, A122. doi:10.1051/0004-6361/201321231
Roth, N. X., Milam, S. N., Cordiner, M. A., Bockelée-Morvan, D., Biver, N., Boissier, J., et al. (2021). Leveraging the ALMA atacama compact array for cometary science: an interferometric survey of comet C/2015 ER61 (PanSTARRS) and evidence for a distributed source of carbon monosulfide. Astrophysical J. 921, 14. doi:10.3847/1538-4357/ac0441
Röttgering, H. (2003). LOFAR, a new low frequency radio telescope. New astron. Rev. 47, 405–409. doi:10.1016/s1387-6473(03)00057-5
Roueff, E., and Lique, F. (2013). Molecular excitation in the interstellar medium: recent advances in collisional, radiative, and chemical processes. Chem. Rev. 113, 8906–8938. doi:10.1021/cr400145a
Schaefer, J., and Lester Jr, W. A. (1975). Theoretical study of inelastic scattering of H2 by Li+ on SCF and CI potential energy surfaces. J. Chem. Phys. 62, 1913–1924. doi:10.1063/1.430678
Selim, T., Christianen, A., van der Avoird, A., and Groenenboom, G. C. (2021). Multi-channel distorted-wave born approximation for rovibrational transition rates in molecular collisions. J. Chem. Phys. 155, 034105. doi:10.1063/5.0058576
Selim, T., van der Avoird, A., and Groenenboom, G. C. (2022). Efficient computational methods for rovibrational transition rates in molecular collisions. J. Chem. Phys. 157, 064105. doi:10.1063/5.0102224
Selim, T., Van der Avoird, A., and Groenenboom, G. C. (2023). State-to-state rovibrational transition rates for CO2 in the bend mode in collisions with He atoms. J. Chem. Phys. 159, 164310. doi:10.1063/5.0174787
Semenov, A., and Babikov, D. (2017). MQCT. I. Inelastic scattering of two asymmetric-top rotors with application to H2O + H2O. J. Phys. Chem. A 121, 4855–4867. doi:10.1021/acs.jpca.7b03554
Semenov, A., Mandal, B., and Babikov, D. (2020). MQCT: user-ready program for calculations of inelastic scattering of two molecules. Comput. Phys. Commun. 252, 107155. doi:10.1016/j.cpc.2020.107155
Song, M.-Y., Cho, H., Karwasz, G. P., Kokoouline, V., Nakamura, Y., Tennyson, J., et al. (2021). Cross sections for electron collisions with H2O. J. Phys. Chem. Reference Data 50, 023103. doi:10.1063/5.0035315
Stewart, B. A., Stephens, T. N., Lawrence, B. A., and McBane, G. C. (2010). Rovibrational energy transfer in Ne- Li2 (A1Σu+, v= 0): Comparison of experimental data and results from classical and quantum calculations. J. Phys. Chem. A 114, 9875–9885. doi:10.1021/jp103504a
Stoecklin, T., Denis-Alpizar, O., Halvick, P., and Dubernet, M.-L. (2013). Ro-vibrational relaxation of HCN in collisions with He: rigid bender treatment of the bending-rotation interaction. J. Chem. Phys. 139, 124317. doi:10.1063/1.4822296
Stoecklin, T., Denis-Alpizar, O., and Halvick, P. (2015). Rovibrational energy transfer in the He–C3 collision: rigid bender treatment of the bending–rotation interaction and rate coefficients. Mon. Notices R. Astronomical Soc. 449, 3420–3425. doi:10.1093/mnras/stv491
Stoecklin, T., Denis-Alpizar, O., Clergerie, A., Halvick, P., Faure, A., and Scribano, Y. (2019). Rigid-bender close-coupling treatment of the inelastic collisions of H2O with para-H2. J. Phys. Chem. A 123, 5704–5712. doi:10.1021/acs.jpca.9b04052
Stoecklin, T., Cabrera-González, L. D., Denis-Alpizar, O., and Páez-Hernández, D. (2021). A close coupling study of the bending relaxation of H2O by collision with He. J. Chem. Phys. 154, 144307. doi:10.1063/5.0047718
Sun, Z.-F., van Hemert, M. C., Loreau, J., van der Avoird, A., Suits, A. G., and Parker, D. H. (2020). Molecular square dancing in CO–CO collisions. Science 369, 307–309. doi:10.1126/science.aan2729
Tao, L., and Alexander, M. H. (2007). Role of van der Waals resonances in the vibrational relaxation of HF by collisions with H atoms. J. Chem. Phys. 127, 114301. doi:10.1063/1.2766716
Tingay, S., Hancock, P., Wayth, R., Intema, H., Jagannathan, P., and Mooley, K. (2016). A multi-resolution, multi-epoch low radio frequency survey of the Kepler K2 mission Campaign 1 field. Astronomical J. 152, 82. doi:10.3847/0004-6256/152/4/82
Toboła, R., Kłos, J., Lique, F., Chałasiński, G., and Alexander, M. (2007). Rotational excitation and de-excitation of PN molecules by He atoms. Astronomy Astrophysics 468, 1123–1127. doi:10.1051/0004-6361:20077339
Toboła, R., Lique, F., Kłos, J., and Chałasiński, G. (2008). Ro-vibrational excitation of SiS by He. J. Phys. B Atomic, Mol. Opt. Phys. 41, 155702. doi:10.1088/0953-4075/41/15/155702
Tonolo, F., and Alessandrini, S. (2024). Ab initio calculations for astrochemistry. Mem. S. A. It. 95, 77. doi:10.36116/MEMSAIT_95N3.2024.77
Tonolo, F., Bizzocchi, L., Melosso, M., Lique, F., Dore, L., Barone, V., et al. (2021). An improved study of HCO+ and He system: interaction potential, collisional relaxation, and pressure broadening. J. Chem. Phys. 155, 234306. doi:10.1063/5.0075929
Tonolo, F., Lique, F., Melosso, M., Puzzarini, C., and Bizzocchi, L. (2022). Hyperfine resolved rate coefficients of HC17O+ with H2 (j= 0). Mon. Notices R. Astronomical Soc. 516, 2653–2661. doi:10.1093/mnras/stac2394
Tonolo, F., Bizzocchi, L., Rivilla, V., Lique, F., Melosso, M., and Puzzarini, C. (2024). Collisional excitation of PO+ by para-H2: potential energy surface, scattering calculations, and astrophysical applications. Mon. Notices R. Astronomical Soc. 527, 2279–2287. doi:10.1093/mnras/stad3140
Tonolo, F., Jóźwiak, H. J., Bizzocchi, L., Melosso, M., Wcisło, P., Lique, F., et al. (2025a). Experimental and theoretical investigation on N2 pressure-induced coefficients of the lowest rotational transitions of HCN. J. Quantitative Spectrosc. Radiat. Transf. 345, 109521. doi:10.1016/j.jqsrt.2025.109521
Tonolo, F., Quintas-Sánchez, E., Batista-Planas, A., Dawes, R., and Lique, F. (2025b). Collisional excitation of hcn by co to refine the modeling of cometary comae. J. Phys. Chem. A 129, 9583–9590. doi:10.1021/acs.jpca.5c05448
Toscano, J., Lewandowski, H., and Heazlewood, B. R. (2020). Cold and controlled chemical reaction dynamics. Phys. Chem. Chem. Phys. 22, 9180–9194. doi:10.1039/d0cp00931h
Troscompt, N., Faure, A., Wiesenfeld, L., Ceccarelli, C., and Valiron, P. (2009). Rotational excitation of formaldehyde by hydrogen molecules: Ortho-h2co at low temperature. Astronomy Astrophysics 493, 687–696. doi:10.1051/0004-6361:200810712
Valiron, P., Wernli, M., Faure, A., Wiesenfeld, L., Rist, C., Kedžuch, S., et al. (2008). R12-calibrated H2O–H2 interaction: full dimensional and vibrationally averaged potential energy surfaces. J. Chem. Phys. 129, 134306. doi:10.1063/1.2988314
van der Tak, F. F., Lique, F., Faure, A., Black, J. H., and van Dishoeck, E. F. (2020). The Leiden atomic and molecular database (LAMDA): current status, recent updates, and future plans. Atoms 8, 15. doi:10.3390/atoms8020015
van Dishoeck, E., Rocha, W., Slavicinska, K., Francis, L., van Gelder, M., Ray, T., et al. (2025). JWST Observations of Young protoStars (JOYS)-overview of program and early results. Astronomy Astrophysics 699, A361. doi:10.1051/0004-6361/202554444
Van Gelder, M., Ressler, M., Van Dishoeck, E., Nazari, P., Tabone, B., Black, J., et al. (2024). JOYS+: mid-infrared detection of gas-phase SO2 emission in a low-mass protostar-the case of NGC 1333 IRAS 2A: hot core or accretion shock? Astronomy Astrophysics 682, A78. doi:10.1051/0004-6361/202348118
Varandas, A., and Marques, J. (1994). Method for quasiclassical trajectory calculations on potential energy surfaces defined from gradients and Hessians, and model to constrain the energy in vibrational modes. J. Chem. Phys. 100, 1908–1920. doi:10.1063/1.466544
Vorburger, A., Fatemi, S., Galli, A., Liuzzo, L., Poppe, A. R., and Wurz, P. (2022). 3D Monte-Carlo simulation of Ganymede’s water exosphere. Icarus 375, 114810. doi:10.1016/j.icarus.2021.114810
Wickham-Jones, C., Simpson, C., and Clary, D. (1987). Experimental and theoretical determination of rate constants for vibrational relaxation of CO2 and CH3F by He. Chem. Phys. 117, 9–16. doi:10.1016/0301-0104(87)80092-7
Wiesenfeld, L. (2022). Quenching transitions for the rovibrational transitions of water: ortho-H2O in collision with ortho-and para-H2. J. Chem. Phys. 157, 174304. doi:10.1063/5.0102279
Wootten, A., and Thompson, A. R. (2009). The atacama large millimeter/submillimeter array. Proc. IEEE 97, 1463–1471. doi:10.1109/jproc.2009.2020572
Wright, G. S., Rieke, G. H., Colina, L., van Dishoeck, E., Goodson, G., Greene, T., et al. (2004). The JWST MIRI instrument concept. Opt. Infrared, Millim. Space Telesc. 5487, 653–663. doi:10.1117/12.551717
Wright, S. O., Waldmann, I., and Yurchenko, S. N. (2022). Non-local thermal equilibrium spectra of atmospheric molecules for exoplanets. Mon. Notices R. Astronomical Soc. 512, 2911–2924. doi:10.1093/mnras/stac654
Yang, C.-H., Sarma, G., Ter Meulen, J., Parker, D., McBane, G., Wiesenfeld, L., et al. (2010). Communication: mapping water collisions for interstellar space conditions. J. Chem. Phys. 133, 131103. doi:10.1063/1.3475517
Yang, D., Hu, X., Zhang, D. H., and Xie, D. (2018). An improved coupled-states approximation including the nearest neighbor coriolis couplings for diatom-diatom inelastic collision. J. Chem. Phys. 148, 084101. doi:10.1063/1.5010807
Yang, J., Hong, Q., Bartolomei, M., Pirani, F., Coletti, C., Sun, Q., et al. (2025). Quantum-classical rate coefficients for O2+N2 inelastic collisions with very high vibrational levels. Phys. Rev. A 111, 032804. doi:10.1103/physreva.111.032804
Żółtowski, M., Loreau, J., and Lique, F. (2022). Collisional energy transfer in the CO–CO system. Phys. Chem. Chem. Phys. 24, 11910–11918. doi:10.1039/D2CP01065H
Żółtowski, M., Lique, F., Loreau, J., Faure, A., and Cordiner, M. (2023). The excitation of CO in CO-dominated cometary comae. Mon. Notices R. Astronomical Soc. 520, 3887–3894. doi:10.1093/mnras/stad268
Keywords: collision dynamics, databases, rate coefficients, non-LTE, JWST
Citation: Tonolo F (2025) Collisional excitation in space: recent advances and future challenges in the JWST era. Front. Astron. Space Sci. 12:1713849. doi: 10.3389/fspas.2025.1713849
Received: 26 September 2025; Accepted: 20 October 2025;
Published: 06 November 2025.
Edited by:
Joan Enrique-Romero, Leiden University, NetherlandsReviewed by:
Alexandre Faure, UMR5274 Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), FranceCopyright © 2025 Tonolo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Francesca Tonolo, ZnJhbmNlc2NhLnRvbm9sby4xQHVuaXYtcmVubmVzLmZy