Quantum dynamical study of rotational excitations in SiS (X 1Σ+) molecule by H collisions

Abstract

The knowledge of accurate rate coefficients for collisional excitation of molecules by the abundant chemical species like He, H 2 and H is important in modeling the conditions of interstellar medium. In the present paper, we computed the inelastic rotational cross sections and the corresponding rate coefficients of SiS molecule in its ground vibrational state in collisions with atomic hydrogen, H. We computed ab initio two-dimensional (rigid-rotor) potential energy surface for the H + SiS system at high accuracy for this purpose. The excitation cross sections are performed by numerically exact close-coupling quantum mechanical formalism up to collision energy of 2000 cm −1 . The corresponding rate coefficients are obtained in the temperature range 5–300 K.

Recent updates of gas-phase chemical reactions and molecular lines of SiS in CLOUDY

“…It includes energy levels up to J =40. There are 40 radiative and 820 collisional transitions covering a temperature range of 10 to 2000 K. Anusuri (2019) quantum dynamically calculated rotational excitations of SiS with H. It also includes 11 transitions over the temperature range of 5 to 300 K. However, CLOUDY uses collisional data in the LAMDA format, which uses deexcitation rate coefficients. Hence, we calculate the deexcitation rate coefficients from the excitation rate coefficients following the formula, Γ ul = Γ lu × (g l /g u ) × exp(hν/kT ) .…”