Ionic State Relaxation Processes in VUV-Excited Polyatomic Molecules. Issue 5 (1983)

• Record Type: Journal Article
• Authors: Leach, Sydney; Dujardin, Gérald
• Is Part Of: Laser chemistry. Volume 2:Issue 5/6(1983)
• Page Start: 285
• Page End: 307
• Publication Date: 1983
• Subjects: Lasers in chemistry -- Periodicals; 542.8
• DOI: 10.1155/LC.2.285
• Languages: English
• ISSNs: 0278-6273

Abstract

Abstract : Advantages of molecular ions for the study of electronic radiationless transitions are discussed. Several coincidence techniques for measuring key relaxation parameters are briefly described. The different cases of radiationless transition studies of molecular ions are outlined and examples mentioned. Coincidence measurements between threshold photoelectrons and ion fluorescence photons emitted by VUV-excited hexafluorobenzene are presented. The radiative, k r, and nonradiative, k n r, relaxation rates for specific vibrational levels in theB ∼ 2 A 2 u andC ∼ 2 B 2 u states ofC 6 F 6 + are derived from the measured lifetimes and quantum yields of ion fluorescence. Thek r rate for excitation of theC ∼, 0° level is found to be about 25% of that for theB ∼ 2 A 2 u state wherek r = (18±3) × 10 6 s −1 . Thek n r rates for the1 n and1 n 2 1 progressions in theB ∼ state increase with n but exhibit a mode selective behavior. Model calculations ofk n r confirm the mode selectivity. These calculations were carried out on a noncommunicating, harmonic oscillator basis. Progressive deviations between experimental and calculated results are interpreted as indicating the gradual onset of vibrational redistribution with increasing vibrational energy. The results illustrate a new method for demonstrating the growing in of intramolecular vibrational relaxation.