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

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(ùA?) 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.