IR spectroscopy and dynamics of a strongly vibrationally excited polyatomic molecule: CF3I

Abstract

The photodissociation technique was used to measure the linear IR absorption spectrum (ν1 and ν4 modes) of rotationally jet-cooled CF3I molecules with vibrational energy E≈D≈19000 cm-1, where D is the dissociation threshold. The dissociation yield of CF3I in the molecular beam was determined by resonant multiphoton ionization of atoms. A narrow resonance with a halfwidth γ<3 cm-1 was observed for the first time in the IR spectrum of a highly excited molecule. The ν1 band revealed Fermiresonance structure, which provides evidence for the presence of beats accompanying the intramolecular vibrational relaxation. Analysis of the ν4 band shape showed that intramolecular broadening of the IR spectrum of a highly excited molecule can be related not only to energy and phase relaxation processes but also to intramolecular inhomogeneous broadening. © 1988.