Assignments and predictions of optically pumped far infrared laser lines in C-13 methanol

Abstract

In this work, the high resolution infrared (IR) spectrum of C-13 substituted methyl alcohol corresponding to the C-O stretch vibration and far infrared (FIR) spectrum corresponding to the torsional-rotational transitions have been recorded using a Fourier transform spectrometer. The results of the detailed analysis on the spectra have been applied to proposed new assignments of FIR laser lines pumped by the 9P(34) CO₂ laser line. These assignments involve highly interacted first excited C-O stretch vibrational state. The assignments are supported by closed combination loops of accurately measured IR and FIR transitions. The analysis also yielded accurate frequencies for seventeen potential FIR laser lines in C-13 methanol. The spectral data relevant to this work are presented. The FIR absorption spectroscopic study allowed us to evaluate the leading torsional-rotational molecular parameters for ¹³CH₃OH in the vibrational ground state. In addition, comments are also made on the identification of FIR laser lines in ¹³CD₃OH pumped by the 10P(24) CO₂ laser line. The results will be useful for a precise model of the Hamiltonian for excited C-O stretching state.