- Measurements of vibration and rotation CARS spectra are reported for several liquids and vapors. Calculations of the observed bandshapes were carried out and forms for vibrational and orientational correlation functions extracted from the data.
The effect of the electronic susceptibility on polarized spectra of the (nu)(,2) Fermi resonant bending mode in liquid carbon tetrachloride was investigated. The heights of peaks arising from the various isotopes are determined primarily by interference effects in the imaginary susceptibility. A value of 6.0 (+OR-) 0.8 picosec was measured for the vibrational correlation time, with isotope splitting equal to 3.05 (+OR-) 0.05 cm('-1).
CARS spectra of the (nu)(,3) symmetric stretch in liquid methyl iodide were obtained. Correlation times for the polarized (1.9 (+OR-) 0.1 picosec) and the depolarized (1.0 (+OR-) 0.1 picosec) spectra are reported, along with estimates of the third-order electronic susceptibility (1.9 x 10('-12) and 1.3 x 10('-12) cm('3)/erg for polarized and depolarized, respectively).
The CARS Q-branch of N(,2) was measured as a function of the gas density. Analysis of both linewidth data and the shift of vibrational frequency with density led to a value of 0.022 cm('-1)/amagat for the density dependence of collisional dephasing of the vibration. A theory concerning the density and linewidth dependence of CARS intensities was tested, but failed to account for the experimental results. Explanations for this discrepancy are suggested.
A novel approach for obtaining low frequency CARS spectra is described. Applicable to any Raman mode involving an anisotropy in the polarizability, the method was used to obtain the pure rotational spectrum of atmospheric N(,2) and O(,2). The intensity distribution, which differs significantly from spontaneous Raman, is in agreement with the theoretical calculations.
Polarized and depolarized spectra were measured for the (nu)(,1) symmetric stretch in carbon dioxide at a series of densities. The frequency shift coefficient (0.011 cm('-1)/amagat) and vibrational collision cross-section (7.5 (ANGSTROM)('2)) obtained from the polarized band widths are used to estimate the magnitude of the phase shifts introduced into the vibration by collisions. Depolarized spectra were shown to agree with calculations based on the J-diffusion model for reorientation. Values are reported for the reorientation cross-section (84 (ANGSTROM)('2)) and for the density dependence of the angular momentum correlation time and the electronic susceptibility.
The experimental difficulties as well as analytical advantages of CARS are discussed.
- Dissertation Note:
- Ph.D. The Pennsylvania State University 1980.
- Source: Dissertation Abstracts International, Volume: 41-05, Section: B, page: 1781.
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