Communication: Selection rules for tunneling splitting of vibrationally excited levels

Abstract

Five symmetry-based selection rules are formulated that relate the tunneling splitting of a vibrationally excited level to that of the ground level in molecules with a symmetric double-minimum potential. The rules, which explain why excited levels frequently have smaller splittings than zero-point levels, are used to interpret the observed and calculated splittings in malonaldehyde. © 2013 AIP Publishing LLC.