Rotationally resolved photoelectron spectra in resonance enhanced multiphoton ionization of SiF

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Abstract
Results of calculations of rotationally resolved photoelectron spectra for resonance enhanced multiphoton ionization (REMPI) of SiF via the B 2Σ+ (4sσ), C″ 2Σ+ (4pσ), and C′ 2Π (4pπ) Rydberg states are reported. In addition to the expected ΔN=even peaks, unusually strong ΔN=±1 transitions are predicted for photoionization of the B 2Σ+ state. These unusual transitions are due to even angular momentum components of the photoelectron matrix element and arise from the formation of Cooper minima in the ionization channels and strong l mixing in the electronic continuum induced by the nonspherical molecular ion potential. Unexpected ΔN=0,±2 transitions, due to odd wave contributions to the photoelectron matrix element, are also predicted for photoionization of the C″ 2Σ+ state. Asymmetrical ion distributions with respect to ΔN=0 are also predicted for the C′ 2Π state. Cooper minima are predicted to occur in the l=2 wave of the kπ photoelectron channel for the B state and in the l=4 wave of the kσ and kπ channels for the C″ state. Photoelectron angular distributions provide further insight into the photoionization dynamics.