Computational Study of the Rovibrational Spectra of CH2D+ and CHD2+

Abstract

In this paper, we present rovibrational energy levels of CH2D+ and CHD2+. They are computed with a large basis and the Lanczos algorithm. CH2D+ and CHD2+ are believed to play an important role in interstellar space, but so far, there are no definitive observations. The predictions of this paper should facilitate detection. For CH2D+, two CH stretch bands have been studied at high resolution. Compared to our calculated energies, the root-mean-square error is 0.08 cm–1. For CHD2+, one CH stretch band has been studied at high resolution. Compared to our calculated energies, the root-mean-square error is 0.5 cm–1. Errors are larger, for both isotopologues, for bend states. We attribute these errors to the potential energy surface. Wave function and probability distribution plots are used to make assignments. The ν1 band of CHD2+ is significantly perturbed, and according to our calculations, the 3ν3 state is closest and might be the most important perturber.