The spectroscopy, photophysics and photodissociation dynamics of jet-cooled CF3NO[Ã(n, π*)]

Julie A. Dyet, M. R S McCoustra, Josef Pfab

Research output: Contribution to journalArticle

Abstract

The LIF excitation spectrum of jet-cooled CF3NO in the visible has been reinterpreted and the torsional structure has been analysed in detail yielding a V'3 barrier to internal rotation of 601.5 cm-1. The predissociation dynamics of jet-cooled CF3NO(Ã1A?) have been re-examined using single vibranic level excitation with a pulsed dye laser and fluorescence decay measurements. Quantum beats and biexponential fluorescence decay behaviour indicate that all levels of the S1(n, p*) state are coupled to levels of the T1 state. The NO photofragment yield spectrum indicates that vibrations with CNO bending character act as promoting modes for the radiationless transition out of S1. Rotational distributions of the nascent NO photoproduct have been characterised in detail and are found to deviate little from statistical distributions, but the F2/F1 spin-orbit branching ratio is very non-statistical, favouring the lower 2?1/2 state of NO. The threshold for the dissociation of CF3NO(D0) and the electronic origin of the à ? X~ transition (T00) have been redetermined and are found to coincide (D0 = 13 980 ± 60 cm-1, T00 = 13 929.7 cm-1). Intersystem crossing and the T1 state are found to be important in the predissociation dynamics of all but the lowest Ã-state levels.

Original languageEnglish
Pages (from-to)463-482
Number of pages20
JournalJournal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics
Volume84
Issue number5
DOIs
Publication statusPublished - 1988

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