Observation by ICLAS VeCSEL technique, and rotational analysis, of the ΔvGeH=5 stretching vibrational overtone of H370GeD

Abstract The fourth GeH stretching overtone band of monoisotopic H 3 70 GeD at 9877 cm −1 has been recorded by ICLAS VeCSEL technique with a path length equivalent to 26 km. The (500 A 1 / E ) band has been observed and rotationally analyzed up to J ′ =18. The band was shown to be essentially unperturbed except some high J states. The assigned transitions were fitted, with σ (Fit) ca. 6.5 × 10 −3  cm −1 . While eight refined parameters were needed up to J ′ max =14, six quartic centrifugal distortion constants were refined in addition for the larger body of 829 data with J ′ max =18. The (500 A 1 / E ) parameters of H 3 70 GeD perfectly fulfill the theoretical relations valid at the local mode limit, and they fit into the series for other ( n 00 A 1 / E ) levels ( n =2, 3, 6, 7, and 8). A transition moment ratio M ( A 1 ): M ( E )=0.25 was found to be in best agreement with the observed spectrum, only high J ( J ′ ⩾13) transitions being evidently sensitive to this ratio.