title: Observation of the predissociated, quasilinear B(1A') state of CHF by optical-optical double resonance.
abstract: We report the first observation of the predissociative B state of a halocarbene molecule. Rovibronic energy levels were measured in the B(1A') state of CHF by fluorescence dip detected optical-optical double resonance spectroscopy via the A state. The origin was found to lie 30 817.4 cm-1 above the zero point level of the X state. Rotational transitions within six purely bending states, and states involving one or two quanta of CF-stretch were observed, including the vibrational angular momentum components. Interpretation of the spectrum, with support of ab initio calculations, shows that CHF is quasilinear in the B state with a small (-200 cm-1) barrier to linearity which lies below the zero-point level. The rotational constant, B=1.04 to 1.09 cm-1, depending on vibrational state, again in good agreement with theory. All observed B state levels were predissociative, as evidenced by Lorentzian line broadening. Linewidths varied with initial state from 0.7-10.8 cm-1, corresponding to excited state lifetimes of 0.5-8 ps.
authors.affiliation: Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, USA.
authors.forename: Chong
authors.initials: C
authors.lastname: Tao
authors.forename: Scott A
authors.initials: SA
authors.lastname: Reid
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Schmidt
authors.forename: Scott H
authors.initials: SH
authors.lastname: Kable