Coherent Raman scattering in high-pressure/high-temperature fluids: An overview

Conference · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6449916

Schmidt, S C; Moore, D S

The present understanding of high-pressure/high-temperature dense-fluid behavior is derived almost exclusively from hydrodynamic and thermodynamic measurements. Such results average over the microscopic aspects of the materials and are, therefore, insufficient for a complete understanding of fluid behavior. At the present, dense-fluid models can be verified only to the extend that they agree with the macroscopic measurements. Recently, using stimulated Raman scattering, Raman induced Kerr effect scattering, and coherent anti-Stokes Raman scattering, we have been able to probe some of the microscopic phenomenology of these dense fluids. In this paper, we discuss primarily the use of CARS in conjunction with a two-stage light-gas gun to obtain vibrational spectra of shock-compressed liquid N{sub 2}, O{sub 2}, CO, their mixtures, CH{sub 3}NO{sub 2}, and N{sub 2}O. These experimental spectra are compared to synthetic spectra calculated using a semiclassical model for CARS intensities and best fit vibrational frequencies, peak Raman susceptibilities, and Raman linewidths. For O{sub 2}, the possibility of resonance enhancement from collision-induced absorption is addressed. Shifts in the vibrational frequencies reflect the influence of increased density and temperature on the intramolecular motion. The derived parameters suggest thermal equilibrium of the vibrational levels is established less than a few nanoseconds after shock passage. Vibrational temperatures are obtained that agree with those derived from equation-of-state calculations. Measured linewidths suggest that vibrational dephasing times have decreased to subpicosecond values at the highest shock pressures.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/AD
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6449916
• Report Number(s): LA-UR-90-2982; CONF-9009260-1; ON: DE91000438; TRN: 91-000039
• Resource Relation: Conference: International symposium on coherent Raman spectroscopy, Samarkand (USSR), 18-20 Sep 1990
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
LIQUIDS
RAMAN SPECTROSCOPY
CHEMICAL REACTIONS
COMPRESSION
ENERGY TRANSFER
IMPACT SHOCK
KERR EFFECT
PRESSURE DEPENDENCE
RAMAN EFFECT
SCATTERING
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
ULTRAHIGH TEMPERATURE
VERY HIGH PRESSURE
VIBRATIONAL STATES
DIELECTRIC PROPERTIES
ELECTRICAL PROPERTIES
ENERGY LEVELS
EXCITED STATES
FLUIDS
LASER SPECTROSCOPY
PHYSICAL PROPERTIES
SPECTROSCOPY
656002* - Condensed Matter Physics- General Techniques in Condensed Matter- (1987-)