Laboratory studies of astrophysical molecules

There is growing evidence that the molecules necessary for the evolution of life on earth arrived from the interstellar medium. The study of these molecules is therefore of great current interest. Two major types of signals from interstellar space, so-called unidentified interstellar infrared emission bands and the diffuse interstellar absorption bands, have intrigued and puzzled astrochemists for decades. This work has been concentrated on how to contribute to an understanding of the origins of these perplexing signals from space and help identify other molecules that may exist in outer space. Matrix isolation spectroscopy (infrared and ultraviolet-visible) combined with theoretical calculations has been employed throughout this research.;Fourier transform infrared absorption spectroscopic measurements, aided by theoretical calculations and 13C-isotope shifts, have led to the identification of eight heretofore unknown CnS m clusters: C2S, C6S, C7S, C7S2, C9S2, C11S 2, C13S2, and C15S2. Infrared absorption studies of xenon polycarbon clusters aid in understanding the special electronic structure and reactivity of carbon clusters, which might be associated with the formation mechanism of Buckyball (C60). Reaction of C 3 with benzene and ammonia might be involved in the formation of more complex molecular structures, including polycyclic aromatic hydrocarbons (PAHs) and biomolecules such as the amino acids.;High resolution vibrational and electronic spectra of neutral dibenzo[b,def]chrysene and its ions in 12 K argon matrices have been recorded. Spectral assignments were supported by high level theoretical calculations. A mixture of the neutral and ionic infrared spectra of dibenzo[b,def]chrysene resembles the unidentified IR bands in the reflection nebula NGC 7023. Anharmonic frequency calculations for neutral and cationic naphthalene, phenanthrene and anthracene using density functional theory have been carried out for the first time, and the results reveal that anharmonic analysis is significant for the C-H stretching modes of neutral PAHs, but harmonic computation is precise enough for the infrared active vibrational analysis of PAH cations. Anharmonic computation might be important for the Raman active vibrational modes.