Raman study of vibrational dephasing in liquid CH/sub 3/CN and CD/sub 3/CN

Journal Article · Fri Apr 01 04:00:00 EST 1977 · J. Chem. Phys.; (United States)

OSTI ID:7310332

Schroeder, J; Schiemann, V H; Sharko, P T; Jonas, J

The Raman line shapes of the ..nu../sub 1/(a/sub 1/) C--H and C--D fundamentals in liquid acetonitrile and acetonitrile-d/sub 3/ have been measured as a function of pressure up to 4 kbar within the temperature interval 30--120 degreeC. Densities have also been determined. From the isotropic component of the vibrational Raman band shape the vibrational relaxation times have been obtained as a function of temperature and pressure (density). The experimental results can be summarized as follows: (i) as T increases at constant density rho, the vibrational relaxation rate (tau/sub vib/)/sup -1/ increases; (ii) at constant T as density is raised tau/sub vib//sup -1/ increases; (iii) at constant pressure the T increase produces higher tau/sub vib//sup -1/, however, the change is more pronounced for the CD/sub 3/CN liquid. Isotopic dilution studies of the CH/sub 3/CN/CD/sub 3/CN mixtures shows no significant effect on (tau/sub vib//sup -1/). The experimental data are interpreted in terms of the Kubo stochastic line shape theory and the dephasing model of Fischer and Laubereau. The results based on Kubo formalism indicate that dephasing is the dominant relaxation mechanism and that the modulation is fast. The isolated binary collision model proposed by Fischer and Laubereau for vibrational dephasing reproduces the essential features of the density and temperature dependence of the (tau/sub vib/)/sup -1/ and suggests that pure dephasing is the dominant broadening mechanism for the isotropic line shapes studied. In the calculation the elastic collision times were approximated by the Enskog relaxation times.

• Research Organization: Department of Chemistry, School of Chemical Sciences and Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801
• OSTI ID: 7310332
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 66:7; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
DEUTERIUM
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
FLUIDS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
LIQUIDS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
RAMAN EFFECT
RELAXATION
STABLE ISOTOPES
VERY HIGH PRESSURE
VIBRATIONAL STATES