A theoretical study of the electronic spectroscopy of the SiF3 radical

A recent vacuum-UV fluorescence spectrum of SiF4 [H. Biehl, K.J. Boyle, D.P. Seccombe, D.M. Smith, R.P. Tuckett, K.R. Yoxall, H. Baumgärtel, H.W. Jochims, J. Chem. Phys. 107 (1997) 720] has yielded information about the decay of electronically excited states of neutral fragments and the parent molecular cation. Emission in the visible region (λ>380 nm) has been observed for an excitation energy of 13.0 eV with a lifetime of 3.9 ns, but the emitter was not assigned. Ab initio CASSCF calculations show that the observed emission is due to the à 2A1–X̃ 2A1 transition in the SiF3 radical. The experimental lifetime, however, is too short to be attributed to this radiative process. We suggest that the lifetime is dominated by rapid internal conversion of SiF3 à 2A1 into high vibrational levels of the ground state.