Ro-vibrational levels of acetylene isotopologues calculated from new potential energy surface

Abstract

Ro-vibrational energy levels of acetylene isotopologues are reported using variational nuclear motion calculations from empirically optimized full six-dimensional potential energy surface (PES) in the ground electronic state. This surface is based on pure ab initio PES of H12C12CH which took into account the triple, quadruple and quintuple excitations as well as relativistic and diagonal Born-Oppenheimer corrections (DBOC). Variational calculations of the motion of nuclei for all isotopologues were carried out using one exact kinetic energy operator in which only the masses of the atoms were changed. Experimental values of 1529 ro-vibrational levels up to J = 10 of the main isotopologue were used to empirically adjust some 58 lower-order parameters of the PES. The unweighted average RMS for empirically optimized PES is 0.0953 cm−1. Ro-vibrational energy levels of H12C12CH, H13C13CH, D12C12CD, D13C13CD, H12C13CH, H12C12CD, H12C13CD, H13C12CD, D12C13CD up to J = 10 were calculated in the ground electronic state. Calculated ro-vibrational energy levels of H12C12CH, H13C13CH, D12C12CD, H12C13CH, H12C12CD isotopologues were compared with high precision empirical energy levels available in literature.