Theoretical study of the HeH (B 2Π) fluorescence and predissociation

Abstract

The most recent HeH potential energy curves and dipole transition moments by Theodorakopoulos and co-workers are employed to study radiative and nonradiative transitions from the bound B 2Π state to the repulsive X 2Σ + state. The emission spectra A ν′ ( v) and the radiative lifetimes τ r B,ν′ are calculated for B, ν′ = 0–8→X the Franck-Condon semiclassical approximation. The predissociative lifetimes τ p B(ν′, N′ of the B 2Π, ν′ = 0–10, N′ = 1–10 levels for 4HeH, 4HeD, 3HeD are obtained by employing the Fermi golden rule and the rotational coupling matrix elements by Kubach and co-workers. The calculated results for the emission spectra and the τ r B,ν′, ν′ ⩾6, τ p B(ν′ ⩾ 5, N′) quantities are novel. Our results confirm earlier theoretical conclusions about predominantly predissociative decay of the B 2Π + state, contradicting to the experimental inference. The nature of this disagreement is discussed and it is shown to be an illusionary one. Special attention is paid to the τ p B(ν′, N′) dependence on the rotational coupling matrix elements.