Vibrationally excited states of 1H- and 2H-1,2,3-triazole isotopologues analyzed by millimeter-wave and high-resolution infrared spectroscopy with approximate state-specific quartic distortion constants

摘要

In this work, we present the spectral analysis of 1H- and 2H-1,2,3-triazole vibrationally excited states alongside provisional and practical computational predictions of the excited-state quartic centrifugal distortion constants. The low-energy fundamental vibrational states of 1H-1,2,3-triazole and five of its deuteriated isotopologues (1-H-2-, 4-H-2-, 5-H-2-, 4,5-H-2-, and 1,4,5-H-2-1H-1,2,3-triazole), as well as those of 2H-1,2,3-triazole and five of its deuteriated isotopologues (2-H-2-, 4-H-2-, 2,4-H-2-, 4,5-H-2-, and 2,4,5-H-2-2H-1,2,3-triazole), are studied using millimeter-wave spectroscopy in the 130-375 GHz frequency region. The normal and 2-H-2-isotopologues of 2H-1,2,3-triazole are also analyzed using high-resolution infrared spectroscopy, determining the precise energies of three of their low-energy fundamental states. The resulting spectroscopic constants for each of the vibrationally excited states are reported for the first time. Coupled-cluster vibration-rotation interaction constants are compared with each of their experimentally determined values, often showing agreement within 500 kHz. Newly available coupled-cluster predictions of the excited-state quartic centrifugal distortion constants based on fourth-order vibrational perturbation theory are benchmarked using a large number of the 1,2,3-triazole tautomer isotopologues and vibrationally excited states studied.