Radiative dissociation and predissociation in HeH and NeH: A theoretical treatment using square-integrable functions

A variational method has been employed for the calculation of the rates of radiative and nonradiative decay of excited states of HeH and NeH. The calculated predissociation rates for the A ${}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state of HeH are larger than the corresponding radiative dissociation rates by about 5 orders of magnitude. For the other excited states of HeH, the predissociation rates are larger by 1–2 orders of magnitude. The theoretical lifetimes of the v=0 level of the A ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$, ${\mathit{B}}^2$Π, C ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$, D ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$, and E ${}_{}{}^2{}_{}{}^{}\mathrm{\Pi }$ states of HeH are 1.2 ps, 17.8 ns, 1 ns, 0.65 ns, and 31 ns, respectively. In NeH, the calculated rate of predissociation of the A ${}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ state is comparable to that of radiative dissociation, while for C ${}_{}{}^2{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$ radiative dissociation has a higher rate than predissociation. The theoretical lifetimes of the A ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$, B ${}_{}{}^2{}_{}{}^{}\mathrm{\Pi }$, and C ${}_{}{}^2{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$ states of NeH (for v=0) are 8.8, 6.0, and 6.9 ns, respectively.