# ABSOLUTE CROSS SECTIONS FOR VIBRATIONAL ENERGY TRANSFER IN THE QUASI-CONTINUUM OF PARA-DIFLUOROBENZENE.

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 Title: ABSOLUTE CROSS SECTIONS FOR VIBRATIONAL ENERGY TRANSFER IN THE QUASI-CONTINUUM OF PARA-DIFLUOROBENZENE. Creators: Tasic, Uros S.; Stone, Todd A.; Parmenter, C. S. Issue Date: 2000 Publisher: Ohio State University Abstract: These experiments yield basic information for kinetic models of the activation/deactivation step of thermal unimolecular reactions. For these highly excited vibrational levels where the high state density approaches a quasi-continuum and where state mixing is significant, a special technique based on oxygen fluorescence quenching $(chemical timing)^{a}$ is used. Absolute cross sections are measured for vibrational energy transfer (VET) from a wide range of $S_{1}$ levels of para-difluorobenzene ( pDFB) as it undergoes single collisions with rare gases. The highest region so far studied has densities of about $10^{4}$ levels per $cm^{-1}$. The study involves preparing pDFB in a narrow vibrational region and monitoring fluorescence as VET with Ar occurs into a field of surrounding vibrational levels. All of the cross sections so far observed are less than the Lennard-Jones value that is often assumed for modeling the unimolecular problem. Some exceed hard sphere values. Description: $^{a}$R. A. Coveleskie, D.A. Dolson, and C.S. Parmenter. J. Phys. Chem., 89, 645 (1985). Author Institution: Department of Chemistry, Indiana University URI: http://hdl.handle.net/1811/19708 Other Identifiers: 2000-MI-11