COMPARISON BETWEEN THEORY AND EXPERIMENT FOR EXCITED STATES OF MOLECULAR HYDROGEN

Abstract

The excited $^{1}\Sigma_{g}^{+}$ states of the $H_{3}$ molecule are affected by strong nonadiabatic coupling. The interaction of the doubly excited $i \sigma_{u}{^{2}}$ configuration with Rydberg configurations $\sigma_{g}$ gives rise to the double-minimum electronic energy curves of the states $EF (2s\sigma_{g}2{^{1}}\sigma_{g}^{+}),GK (3d\sigma_{g}, 3{^{1}}\sigma_{g}^{+})$, and to the higher lying curves of the states $i{^{1}}\sigma_{g}^{+}(i=4,5,\ldots)$ which continue the $ns\sigma$ and $nd\sigma$ series. The vibrations of all of these adiabatic states $i^{1}\Sigma_{g}^{+}$ are mutually coupled via the operators $+2 4$ (up to $\simeq 30 cm^{-1}$). This has been investigated with the aid of Quadrelli's model as well as by comparing the ab-initio results for $H_{2}$ and $D_{2}$. For the $v=0$ level of the EF state the nonadiabatic energy shift is smaller than $0.1cm^{-1}$; the $2cm^{-1}$; error of the adiabatic calculation is of magnitude comparable to ab-initio results on other excited states of $H_{2}$.