Theoretical investigations of the electronic states and electron scattering cross-sections of thiazole (C3H3NS)

Abstract

We present here theoretical investigations of electronic states and electron scattering cross-sections of the thiazole molecule. Spectroscopic calculations are performed on ground and excited states of thiazole using density functional theory (DFT) and time dependent DFT, while the electron impact scattering calculations are carried out using ab initio R-Matrix method. The optimized geometrical parameters and computed vibrational frequencies of neutral and cationic thiazole molecule are in good agreement with earlier work. Detailed comparison of the present computed vertical excitation energies with earlier experimental studies helps to confirm several of the earlier assigned Rydberg transitions while leading to revised assignments for some of the earlier observed peaks. Extensive electron scattering cross-sectional data; Elastic cross-sections include symmetry decomposition, differential and momentum transfer cross-sections while inelastic cross-sectional data comprises of discrete electronic excitations and ionization cross-sections along with their rate-coefficients. According to literature survey, this is the first report of cross-section data and rate coefficients for inelastic processes. A comparison of the total cross-sectional (TCS) data of thiazole with the TCS data of the isoelectronic thiophene molecule reveals the overall TCS values being higher in thiazole, as expected due to its higher dipole moment. Further, resonant peaks in the TCS are observed to be shifted to lower energies in thiazole as compared to thiophene, which is attributed to the higher electronegativity of the N atom as compared to the CH group in thiophene. For the first time, a comprehensive spectroscopic and electron scattering study of thiazole is summarized in this paper.