Knowledge Bank

The valence slate dependence of the Ar - HF interaction potential is extended to $vHF=4$. Three new $ArHF(vHF=4)$ states, (4000), (4100), and (4110), are observed between 14780 and $14880cm-1$ using intracavity laser induced fluorescence. The spectroscopic constants of these states are: (4000) $vo=14783.60323(30)cm-1$, and $B=0.1036068(68)cm-1$; (4100) $vo=14867.41906(70)cm-1$, $B=0.102612(27)cm-1$; and $(4110)\nu o=14875.04673(31)cm-1$, $B=0.1012823(73)cm-1$ respectively. In conjunction with the previous ArHF results $(vHF=0-3)$, the spectral red shifts of ArHF (v000) increase more rapidly than linearly, from $9.654cm-1$ at v=1 to $48.024cm-1$ at v=4. The rotational constants of $ArHF(v000)$ increase essentially linearly, with $vHF$, noticeably increased by 1.30% (40 MHz) at v=4. The classical turning point of HF is extended by $0.4\backslash AA$ from $re$ at v=4, showing no evidence for Ar-H repulsion. The spectral red shift for linear hydrogen bonded Ar-HF (v000) indicates a strong enhancement of binding energy upon HF valence bond elongation, while the rotational constant indicate an almost surprising decrease in heavy atom separation. Both the T-shaped ArHF (v 110) and anti-linear Ar-FH(v100), however, show very little dependence of binding energy upon $vHF$ valence excitation. These observations are in good accord with the ab initio calculations of the Ar-HF intermolecular potential surface.