Modelling of the 2ν1-ν1 and ν1 band transitions of 13CH4 using high resolution Raman spectroscopy measurements

Abstract

Abstract The pump-probe technique for investigating vibrationally excited states via high resolution Raman spectroscopy was applied to 13CH4 methane isotopologue. The dipole transitions between A1 totally symmetric vibrational states are not active in IR spectra but these states can be efficiently studied using selective high resolution Raman spectroscopy. 80 vibration-rotation transitions, most of which belong to the 2ν1– ν1 band have been assigned in the observed Raman spectra reported in this work. Including the Raman transitions in the simultaneous data fit improves the accuracy of the effective Hamiltonian and also rovibrational upper state levels of the ν1, 2ν1 and 2ν3 (A1) bands. A more accurate model of the ν1 vibration-rotation transitions improves the interpretation of the temperature dependence of Raman spectra involving the Pentad and Tetradecad polyads.