- Conference date: 10–13 July 2012
- Location: S. N. Bose National Centre for Basic Sciences, Kolkata, India
This work reports the spectral information of some interstellar complex molecules which could be treated as the precursor molecules for the formation of some bio-molecules in the interstellar medium (ISM). We carry out quantum chemical simulation to consider the Core correlation and vibrational corrections to the rotational constants and centrifugal distortion constants which are computed from harmonic and anharmonic force fields obtained at MP2/6-311G(d,p) level of theory. These precursor molecules could be produced in the gas phase as well as in the ice phase. This prompted use to couple the hydrodynamics of the collapsing phase of the protostar with our reasonably large chemical network including the gas phase as well as the grain phase chemical network, to study the chemical evolution of these species during the collapsing phase of a proto-star. We have noticed the Significant differences between spectroscopy of these species in the gas as well as in ice (water ice) phase due to the solute-solvent elctrostatic interactions. Time dependent density functional theory (TDDFT) is used to study the UV-VIS spectrum of these complexmolecules which are biologically important. Interstellar grain mantle around the dense cloud (> 104 cm−3) mainly composed by 60-70% Water, 5-30% Methanol and 2-20% CO2. So in reality, the ice could be mixed instead of simple water ice. To have an idea about the real spectra, we carry out our simulations for the mixed ice also by considering the actual composition of the above species in interstellar grain mantle. Spectral signatures are found to be significantly shifted with change of the solvent which confirms that the polarization of the solute by the continum has important effects on the absolute and relative solvation energies. Our simulated spectrum are in good agreement with some of the recent experimental result. We expect that our quantum chemical approach along with the hydro-chemical study might be useful for the observer to predict the abundances of some bio-molecules based on the chemical abundances of their precursor molecules.
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