Electron induced chemistry of thiophene

Abstract

A comprehensive theoretical study of electron scattering with thiophene over a wide impact energy range is reported in this article. Total, elastic, differential and momentum transfer cross sections were computed at low energy using an ab initio R-matrix method through QUANTEMOL-N. The R-matrix calculations were carried out using the Complete Active Space–Configuration Integration (CAS–CI) method employing Static Exchange (SE) and Static Exchange plus Polarization (SEP) models. Beyond the ionization threshold, from intermediate to high energy the calculations were carried out using the Spherical Complex Optical Potential (SCOP) formalism. There is a smooth crossover of the two formalisms at the overlap energy, and hence we are able to predict the cross sections over a wide energy range. Apart from the scattering cross section calculations, the other focus was to obtain resonances which are important features at low energy. We observed three prominent structures in the total cross section (TCS) curve. The first peak at 2.5 eV corresponds to the formation of a σ* resonance which is attributed to a Feshbach resonance, in good agreement with earlier predicted experimental and theoretical values of 2.65 eV and 2.82 eV, respectively. The second peak observed at 4.77 eV corresponds to the shape resonance that resembles earlier predicted experimental values of 5 eV and 5.1 eV, which is attributed to ring rupture. The third peak at 8.06 eV is attributed to a core excited shape resonance. There is a lone previous theoretical dataset for the total cross section by da Costa et al. [R. F. da Costa, M. T. do N. Varella, M. Lima, and M. Bettega, 2013, J. Chem. Phys., 138, 194306] from 0 to 6 eV, and no other theoretical or experimental work is reported at low energy to the best of our knowledge. Hence the present work is important to fill the void of scattering data as the earlier work is fragmentary. The differential, momentum transfer and excitation cross sections beyond 6 eV are reported for the first time.