The ν5 band of 12CH 313CH 3: High resolution stimulated Raman spectrum and global three band analysis

Abstract

Rotationally resolved spectrum of 12CH 3 13CH 3 in the region of ν 5 vibrational fundamental (C C stretch) was observed using stimulated Raman spectroscopy. This spectrum was analyzed with data from the ν 12 fundamental and transitions from the ν 6, 2 ν 6– ν 6, and 3 ν 6 torsional bands using a 3-state fit. One torsional component of the ν 5 fundamental is perturbed, interacting with its partner in the ν 6 = 4 of the torsional stack of the ground vibrational state. As for normal ethane, the coupling was successfully modeled using a Fermi-type interaction. The results mirror that of 12CH 3 12CH 3 in that the inclusion of the Fermi-type interaction reduces the required number of terms in the Fourier expansion of the torsional potential for the ground vibrational state from three (in the 2-state fit) to one, only the term in the barrier height is required.