Low Electronic States of Simple Heteropolar Diatomic Molecules: III. Hydrogen and Univalent Metal Halides

Abstract

Electronic structures for the electronic states involved in the near ultraviolet spectra of AX are discussed (X=halogen, A=hydrogen or univalent metal). The upper electron levels involved are mostly among a set of levels $Q {}_{}{}^1{}_{}{}^{}\Pi$ and ${}_{}{}^3{}_{}{}^{}\mathrm{II}$, $T {}_{}{}^3{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$, $V {}_{}{}^1{}_{}{}^{}\Sigma _{}^{+}{}_{}{}^{}$, or their $\Omega -s$ or case $c$ equivalents. Tentative potential energy curves for states $Q$, $T$ and $V$ of HI, AgI, and NaI are shown in Figs. 1-3. It is concluded that the observed HX absorption (continuous) involves the three $Q$ levels corresponding to ${}_{}{}^3{}_{}{}^{}\mathrm{II}_1^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}\mathrm{II}_0^{}{}_{}{}^{}$+, and ${}_{}{}^1{}_{}{}^{}\mathrm{II}$, but with $\Omega -s$ coupling. It is further concluded (in contrast to what is found in the halogen spectra) that the observed absorption goes mainly to the ${}_{}{}^3{}_{}{}^{}\mathrm{II}_1^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}\mathrm{II}$ levels rather than the ${}_{}{}^3{}_{}{}^{}\mathrm{II}_0^{}{}_{}{}^{}$+. The $N$ and $V$ potential energy curves of HX obtained here are compared (see text) with those given by Pauling; for HI there is good agreement, but for HBr, HCl, HF the $V$ curves go increasingly higher than those of Pauling.