title: Kinetically controlled selective ionization study on the efficient collisional energy transfer in the deactivation of highly vibrationally excited trans-stilbene.
abstract: Direct measurements of the gas-phase collisional energy transfer parameters are reported for the deactivation of highly vibrationally excited trans-stilbene molecules, initially prepared with an average energy of about 40 000 cm(-1), in the bath gases argon, CO2, and n-heptane. The method of kinetically controlled selective ionization (KCSI) has been used. Complete experimental collisional transition probability density functions P(E',E) are determined, which are represented by a monoexponential form with a parametric exponent in the argument, P(E',E) proportional to exp[-{(E - E')/(C0 + C1E)}Y] (for downward collisions), well established from earlier KCSI studies. A comparison of the first moments of energy transfer rate constants, kE,1, or of resulting first moments of energy transfer, <DeltaE(E)>, for trans-stilbene with those for azulene and toluene clearly shows the considerably more efficient deactivation of trans-stilbene for all bath gases, presumably due to the much greater number of very low-frequency modes of trans-stilbene. However, on a relative scale this gain in deactivation rate of excited trans-stilbene is clearly collider dependent and decreases distinctly with the growing collision efficiency of the larger bath gas molecules.
authors.affiliation: Institut für Physikalische Chemie, Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Frerichs
authors.forename: Matthias
authors.initials: M
authors.lastname: Hollerbach
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenzer
authors.forename: Klaus
authors.initials: K
authors.lastname: Luther