Picosecond studies of vibrational linewidth broadening in liquids

Technical Report · Tue Mar 01 04:00:00 EST 1983

OSTI ID:6305264

George, S M

The mechanisms of vibrational linewidth broadening in liquids are investigated using picosecond light pulses. Vibrational linewidths in liquids are demonstrated to be both homogeneously and inhomogeneously broadened. The homogeneous broadening is dependent upon rapidly varying processes probably associated with short-range, repulsive collisional interactions between the vibration and neighboring molecules. On the other hand, the inhomogeneous broadening is dependent upon slowly varying, long-range attractive interactions between the vibration and the surrounding local number density. Homogeneous and inhomogeneous broadening linewidths are determined for the symmetric CH/sub 3/-stretching vibration in a variety of liquids at room temperature and in one liquid at a variety of temperatures. A selective excite-and-probe vibrational dephasing experiment based upon transient stimulated Raman scattering in high laser depletion is used to measure T/sub 2/ homogeneous vibrational dephasing times. Inhomogeneous linewidths are shown to be proportional to the width of the distribution of local number densities in the liquid. This correlation suggests that a distribution of different, slowly varying local number densities in a liquid establishes an inhomogeneously broadened distribution of distinct vibrational frequencies. The relative contributions of homogeneous and inhomogeneous broadening are shown to change significantly with temperature. A general theory for excite-and-probe vibrational dephasing experiments performed using transient stimulated Raman scattering in both low and high laser depletion is presented.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6305264
• Report Number(s): LBL-15842; ON: DE83011742
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
ELECTROMAGNETIC RADIATION
FLUIDS
LASER RADIATION
LINE BROADENING
LIQUIDS
OSCILLATIONS
PULSES
RADIATIONS
RAMAN SPECTRA
SPECTRA
TEMPERATURE DEPENDENCE