Time-dependent mass spectra and breakdown graphs: 15—toluene-d8

✍ Scribed by N. Ohmichi; I. Gotkis; L. Steens; C. Lifshitz

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 582 KB
• Volume: 27
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210270407

✦ Synopsis

The ion storage time in the cylindrical trap of a photoionization mass spectrometer has been extended to -500 ma Time-resolved photoionization efficiency (PIE) curves were meaured for [ C,D, I + and I C,D, 1 + for toluene-d, and for the ion-molecule reaction product [ C,D, 1 +. PIE curves were modeled by kQ dependences via RRKM/ QET calculations based on a model by Huang and Dunbar, with critical energy E,, = 213 eV and a lo00 K activation entropy AS* = -14.6 e.u. No energy range was found, even under long storage times, for which [ C,D,I + is pure tropylium, Tr+. The results are interpreted via the case C behaviour in isomerizing ions, due to h e r and co-workers, according to which Tr+ and [ benzyll+, Bz*, are formed at equal rates for energies in exces of both of theii dissociation limits. Dissociation is suppressed at internal energies lower than -2 5 eV due to radiative decay in the infrared region. Dissociations observed at photon energies lower than -113 eV (8.8 eV ionization energy + 2 5 eV internal emrgy) are ascribed to the ofktting effects of an intrinsic kinetic shift of -0.4 eV and the thermal energy distribution in the molecular ions.