About this Research Topic
The interstellar medium (ISM) is the site of a rich chemistry that evolves from simple molecules to complex organic ones. To date, a large number of molecular species (>220) have been detected. Among the detected species are PAHs, and many other organic molecules with a carbon skeleton. Over the last decades, it has been elucidated that not only gas-phase reactions can occur, but also those at the interface of solid surfaces, especially icy dust grains, play a crucial role in the formation of new species.
Although such complex carbon compounds are ubiquitous in many astronomical sources, and influential in the ISM, their precise formation processes and role in the complex molecular chemistry and astrophysics of space remains scarce. The potential of current and upcoming novel satellites such as the impressive suite of instruments James Webb Space Telescope (JWST) offer a unique opportunity and completely novel approach to key astronomical questions.
There is generally much less consensus on the nature of dust and dust-related chemistry than in gas-phase chemistry. This makes dust chemistry a lively field of research, as we do not have all the answers. Furthermore, determination of reaction pathways pertaining to detected species are very challenging due to the possibility of multiple mechanisms including gas phase reactions as well as crucial catalytic effects of ices/dust grains. As the underlying processes remain unclear, many of them are based on chemical intuition and analogous mechanisms of gas phase pathways.
This Research Topic will cover gas-phase chemistry, and gas/dust reactions. The goal is to derive fundamental and molecule-specific parameters (spectroscopic data, reaction and diffusion barriers, chemical rates). This data can then be included in astrochemical models that simulate, for example, the evolution and complexity of ice on typical realistic time scales.
The proposed collection concerns a very important, fundamental and topical subject, in terms of advanced computational techniques, space missions, and sophisticated experimental setups. The combined knowledge of all the experts in these research fields will certainly lead to fruitful new findings and very promising results that can enrich human understanding of the Universe and can help to reveal the origin of life.
From the modelling point of view, spectroscopic constants, energetics, reaction paths, reactive dynamics, and chemical kinetics can be studied. A variety of computational methods, either classical and/or quantum, and dynamical techniques: semi-empirical, reduced dimension, or fully quantum are available to tackle with chemical accuracy the above-mentioned research aims. Rate constants can be predicted using several sophisticated methodologies, such as variants of transition state theory with inclusion of quantum effects, or the Instanton Theory to treat electron transfer in complex systems.
Furthermore, recent progress in experimental techniques has allowed probing with unprecedented details, gas-phase phenomena as well as surface processes: thermal, chemical and photo-induced desorption, diffusion and bulk processes. Experiments use absorption, cavity ringdown, Fourier transform microwave and THz time domain spectroscopy, including synchrotron radiation.
On the observation side, in addition to the Spitzer and Herschel missions, airborne (SOFIA) and ground (ALMA) based facilities provide high-resolution data in the mid and far infrared domains.
Keywords: ISM, astrochemistry and observations, spectroscopy, reaction mechanisms on dust grains, molecular processes, surface science
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