The effect of vibrational motion on the dynamics of shape resonant photoionization of BF₃ leading to the state of

Abstract

We present the results of an experimental and theoretical investigation of vibrationally resolved valence shell photoionization of BF₃ leading to the state of , where vibronic coupling and shape resonances are known to be important. The experimental vibrational branching ratios for multiple quantum excitations of the symmetric stretching mode of the ion as well as for the single vibrational excitation of the asymmetric stretching mode are compared with the predictions of single-channel Schwinger variational calculations performed within the Chase adiabatic approximation to obtain vibrational-state specific cross sections. The presence of a shape resonance in the continuum of symmetry is seen to lead to significant non-Franck–Condon intrachannel vibronic coupling effects. The breakdown in the Franck–Condon approximation is due to the sensitivity to the asymmetric stretching mode of the energy of the resonance and the magnitude of the transition moment for exciting the resonance. However, there are indications that interchannel vibronic coupling effects may also be significant in this system.

Keywords:

• molecular photoionization
• shape resonance

Acknowledgements

EDP and RRL acknowledge that this work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. RRL acknowledges the support of the Robert A. Welch Foundation under grant A-1020. This work was also supported by the Texas A&M University Supercomputing Facility.