The Renner effect in nearly linear molecule, with application to NH2

Abstract

The theory developed by Renner, and Pople and Longuet-Higgins, for vibronic interactions in a triatomic molecule has been extended to allow both component states of an electronic II state to have double minima potentials. The energy levels for this model have been found by diagonalization of a truncated infinite Hamiltonian matrix using a computer. This theory has been applied to the experimental data for NH₂, and it is concluded that the excited state is bent. The equilibrium angle is 144° ± 5°, and the barrier height is 777 ± 100 cm^-1. However, only the lowest vibronic level of the excited state lies below the potential maximum. The complete array of energy levels suggests that the usual Hamiltonian for vibronic interaction overestimates the importance of vibronic effects at large displacements from the linear configuration. Vibronic effects are also shown to be negligible for the lower levels of the ground state of NH₂.