Speaker
Description
In recent years, the detection rate of molecules in the interstellar medium (ISM) has been accelerating (CDMS 2024) [1]. This is in large part thanks to significant advances in detection techniques and astronomical data processing. Nitriles (or cyanides) are among the most abundant chemical species in the ISM. They are key species in prebiotic chemistry and their role in the so-called RNA world. This simple and reactive functional group offers a unique potential to build up more complex molecules such as ribonucleic acids but also nucleobases. In terms of formation and evolution of these molecules, many physico-chemical processes play an important role, such as desorption from interstellar grains, radiative recombination, photolysis, to name only a few. In order to estimate the importance of the latter, one must know, for example, absorption cross sections in the UV and VUV spectral domain. The ubiquitous abundance of nitriles might be due to their photostabilty. In this study we investigate the single photon ionization of two organic nitriles that have been recently detected, namely vinyl cyanoacetylene [2] and methacrylonitrile [3], in the 8 to 15 eV spectral domain. We present ion yield spectra of parent and fragment ions, as well threshold photoelectron spectra. The experiments are completed by quantum-chemical calculations. All results are discussed in the light of the related molecular photodynamics as well as the astrophysical context. Photoionization rates are calculated for typical interstellar radiation fields.
[1] The Cologne database of Molecular Spectrocopy, cdms.astro.uni-koeln.de
[2] K.L.K. Lee et al., Astrophys. J. Lett. 908, L11, (2021).
[3] J. Cernicharo et al., Astron. Astrophys. 663, L5, (2022).
