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The role of molecular spectroscopy in astrophysics and astrochemistry is discussed in the context of the study of large, complex, carbon-bearing molecules, namely, Polycyclic Aromatic Hydrocarbons or PAHs. These molecular species are now thought to be widespread in the interstellar medium in their neutral and ionized forms. Identifying the carriers responsible for unidentified interstellar spectral bands will allow to derive important information on cosmic elemental abundances as well as information on the physical conditions (density, temperature) reigning in specific interstellar environments. These, in turn, are key elements for a correct understanding of the energetic mechanisms that govern the origin and the evolution of the interstellar medium. A multidisciplinary approach - combining astronomical observations with laboratory simulations and theoretical modeling - is required to address these complex issues. Laboratory spectra of several PAHs, isolated at low temperature in inert gas matrices or seeded in a supersonic jet expansion, are discussed here and compared to the astronomical spectra of reddened, early type, stars. The electronic spectroscopy of PAHs in the ultraviolet, visible, and near-infrared domains is reviewed and an assessment of the potential contribution of PAHs to the interstellar extinction in the ultraviolet and in the visible is discussed.

The research conducted during the reporting period is grouped into three sections: 1) Warm molecular gas in the interstellar medium (ISM); 2) Absorption line studies of "cold" molecular clouds; 3) Vaporization of comets around the AGB star IRC+10216.

The research conducted during the reporting period is grouped into three sections: 1) Warm molecular gas in the interstellar medium (ISM); 2) Absorption line studies of "cold" molecular clouds; 3) Vaporization of comets around the AGB star IRC+10216.

There are more than 150 molecules already detected in the Inter stellar medium (ISM). Cyanopolyynes are linearmolecules detected in the ISM by their rotational and vibrational spectra. Here we used GAMESS (General Atomic and Molecular Electronic Structure System), a quantum computation software for obtaining molecular structure and spectra (vibrational) of Cyanopolyynes. We also used graphical visualization program JMOL the nature of different vibrations were studied. Origin software was used for Graphical representation. It is recognized that the Cyanopolyynes have mainly three important intense features that are due to C-H stretch, N≡C and C≡C stretches and C≡C-H bending vibrations. The variations in intensity and frequency of these modes withchain length is studied and discussed.