LOCAL MODE BEHAVIOR IN THE STRETCHING OVERTONES OF GERMANE

Abstract

The Ge-H stretching overtone band near $4155 cm^{-1}$ has been recorded with Doppler-limited resolution, for both natural $GeH_{4}$ and enriched $^{74}GeH_{4}$, using a difference-frequency spectrometer. The structure has been analyzed in terms of a closely-coupled $A_{1} + F_{2}$ pair of bands for each isotopic species. The vibrational modes are best described not as $2\nu_{1}, \nu_{1} +\nu_{3}$ or $2\nu_{3}$ levels but rather as a (2000) local mode cluster. The rotational coupling between the $A_{1}$ and $F_{2}$ substates leads to a complex spectrum, which has been successfully modeled and fitted to around $J=10$ to 12. Over 1650 assignments for the five isotopic species have been fitted with a standard deviation of around $3^{*}10^{-4} cm^{-1}$.