High-Resolution Fourier Transform Spectroscopy of CARBON-13 METHANOL-D(3) with Far-Infrared Laser Analysis

This work is a high-resolution Fourier transform study of the infrared (IR) and far-infrared (FIR) spectra of the ^{13}CD_3OH isotopic species of methanol. The spectroscopic regions investigated include 14-240 cm^ {-1} covering the torsion-rotation ground vibration FIR spectrum, 815-930 cm^{ -1} covering the in-plane ^{13}CD_3-rocking band, 930-1030 cm^{-1} covering the ^{13}C-O stretch band, and 1030-1240 cm^{-1} covering the ^{13}CD _3-deformation band. The results have been applied to the identification and confirmation of reported IR-pump/FIR-laser systems and the prediction of new FIR laser lines. The program may be divided into four parts. The first comprises the analysis of as many absorption lines as possible in the spectroscopic regions mentioned above (~6000 lines for the FIR region, ~2300 for the ^{13}CD_3-rocking band, ~3400 for the ^ {13}C-O stretch band, and ~ 1100 for the ^{13}CD _3-deformation band). All assigned transitions except those of the ^{13}CD _3-deformation band are presented in Appendices to this thesis in ascending order of frequency. Individual series assignments are also available on diskettes in both Macintosh and PC format. The second part consists of the observation and characterization of numerous perturbations in the spectra. These include Fermi resonances between excited vibrational states and the third and fourth excited torsional states of the ground vibrational state, Coriolis interactions between n = 1 of the ^{13}CD _3-rock and n = 0 of the ^{13}CD_3-deformation, and DeltaK = 1 and 2 molecular asymmetry couplings in the ground vibrational state and in the ^{13}CD_3-rocking state. In the third part, state-specific Taylor series expansion parameters have been determined by a least squares fit for each transition series. The origins of the series for the various IR and FIR bands have been fitted to molecular parameters for each vibrational state. Complete sets of b-type constants have been found for the ground and the ^{13}C-O stretch states for the first time. For the ground vibrational state, our results reproduce the observed band origins to approximately the order of the experimental errors for a wide n and K range. For the ^{13}C -O stretch state, the set of b-type parameters obtained from fitting all observed n = 0 band origins allows a theoretical determination of any n = 0 energy level in the ^{13}C-O stretch state, and also gives the size of the downward shifts for the n = 1 energy levels due to the presence of the O-H bending mode lying just above. The torsional barrier heights found for the ground, ^{13}CD_3 -rocking, ^{13}C -O stretch, and ^{13}CD _3-deformation states are 370.21, 482.8, 368.7, and 325 cm^{-1}, respectively. This is about a 30% increase for the ^{13}CD_3-rocking state, and a 12% decrease for the ^ {13}CD_3-deformation state, in going from the ground vibrational state. The fourth and final portion of the program combines the observed FIR and IR data to identify IR-pump/FIR-laser transition systems for ^{13 }CD_3OH. The detailed high-resolution studies have led to assignments for nine further reported IR-pump/FIR-laser systems, most of which have been confirmed with combination frequency loops. Accurate FIR laser frequencies have thereby been obtained from the spectroscopic data. In addition, the results have confirmed two previously proposed FIR laser schemes, and suggest two new potential CO _2 pump lines with five predicted FIR laser line frequencies given accurately from combination frequency loops.