Theoretical Herman-Wallis coefficients for C70 and D70 and the dipole-moment function of HCl

Abstract

Theoretical expressions for the Herman-Wallis coefficients C 7 0 and D 7 0 and a correction term of order 2 B e /ω e times the leading term for C 6 0 have been derived in terms of the Dunham potential-energy parameters and series dipole-moment expansion coefficients by the method of computer algebra. After reviewing previous work on the extraction of the dipole-moment function for HCl from experimental data, the present results are applied to a determination of the series representation up to seventh order in the reduced displacement from the equilibrium internuclear separation. Coefficients for an alternate representation in terms of a Padé approximant are also obtained; this model dipole-moment function should enable one to estimate more accurately the higher overtone and highly excited hot-band intensities since it circumvents the divergence difficulties of the series expansion and has the correct asymptotic behavior at both small and large internuclear separations.