Vibrational levels for the lowest-lying triplet and singlet states of CH2 and NH+2

Abstract

The 30 lowest vibrational energy levels are calculated for the X̃ 3B1 and ã 1A1 states of CH2 and NH+2 for various potential energy surfaces. We include a new surface for the NH+2 triplet state, with predicted fundamentals ν1=3059, ν2=845, and ν3=3360 (expt 3359.9) cm−1. Where possible, results are compared with vibrational levels calculated using two other methods and with experiment. At low energy, the differences between the calculated vibrational levels are due primarily to the choice of potential energy surface. Of secondary importance is the method used to calculate the vibrational energy levels. The differences resulting from the method used are most apparent for cases with a diffuse vibrational wave function or for cases where the bond distance along the minimum energy path depends strongly on the bending angle.