Rotational excitation of sodium hydroxide molecule (NaOH) by helium (He) at low temperature

Abstract

This paper reports the rotational excitation of the alkali sodium hydroxide molecule () by collision with helium atom. We present a new 2D potential energy surface (PES) for NaOH–He van der Waals complex. The PES was computed at the coupled cluster level of theory with single, double and perturbative triple excitation (CCSD(T)) using the aug-cc-pVQZ basis sets for the four atoms with bound functions. A global minimum of −100.15 cm−1 is found at linear geometry He–NaOH and a local minimum of −21.94 cm−1 is located at linear geometry He–HONa. The scattering calculations were performed, via close coupling approach, for a grid of total energies up to 1500 cm−1 to ensure converged state-to-state rate coefficients for kinetic temperatures ranging from 5 K up to 300 K among the first 13 rotational levels. Propensity rules that favor Δj = ±1 transitions are found. These new rates have great potential for NaOH detection in the interstellar medium.