Osnabrück 2002 – wissenschaftliches Programm
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MO: Molekülphysik
MO 19: Poster II (Energietransfer, Reaktionen, Photoionisation, Femtosekundenspektroskopie, ultrakurze Pulse)
MO 19.8: Poster
Donnerstag, 7. März 2002, 17:30–19:30, Schloss
Time-resolved photoelectron spectroscopy of the I− + CH3I symmetric SN2-reaction — •R. Wester, A. E. Bragg, A. V. Davis, and D. M. Neumark — Department of Chemistry, University of California Berkeley, Berkeley CA 94720, USA
The bimolecular symmetric nucleophilic substitution (SN2) reaction of iodine anions with methyl iodide has been studied in real time using femtosecond photoelectron spectroscopy. At time zero a femtosecond pump pulse dissociates the I2− bond in the precursor complex I2−(CH3I), thereby initiating the (SN2) reaction. The reaction dynamics are probed by photodetaching with a second femtosecond pulse and recording the photoelectron kinetic energy spectra for various delay times.
Several dynamical features are observed in the experiment: Within 100 fs of the pump pulse, I− ions are found in the vicinity of CH3I. Part of the I− flux rebounds and pulls away within 1 ps; the remaining flux forms a vibrationally excited I−CH3I complex that decays within tens of picoseconds back to I− + CH3I. These results will be compared to recent theoretical work for the Cl− + CH3Cl reaction.