Vibration-dependent photoelectron angular distributions and branching ratios observed across the Cooper-minimum region of bromobenzene

Powis, Ivan; Patanen, Minna; Antonsson, Egill; Nicolas, Christophe; Miron, Catalin; Holland, David M.P.

Abstract

Vibrational state-resolved photoelectron anisotropy parameters, beta, for the ~X 2B1, ~B 2B2, and ~C2B1 state ionizations of bromobenzene have been recorded at photon energies ranging from 20.5 to 94 eV, so spanning the region of the expected bromine Cooper minimum (CM). The ~X state displays no CM and its beta value is also independent of vibrational level, in accord with the Franck-Condon Approximation. The ~B and ~ C state beta values display the CM to differing degrees, but both show a vibrational dependence that extends well below the obvious CM dip. Calculations are presented that replicate these observations of Franck-Condon Approximation breakdown spanning an extended photon energy range. This is the first demonstration of such wide-ranging breakdown detected in the beta anisotropy parameter in the absence of any resonance. Measured and calculated vibrational branching ratios for these states are also presented. Although the ~B state branching ratios remain constant, in accord with Franck-Condon expectations, the ~X and (especially) the ~C state ratios display weak, quasi-linear variations across the studied range of photon energy, but with no apparent correlation with the CM position.

Citation

Powis, I., Patanen, M., Antonsson, E., Nicolas, C., Miron, C., & Holland, D. M. (2017). Vibration-dependent photoelectron angular distributions and branching ratios observed across the Cooper-minimum region of bromobenzene. Physical Review A, 96(1), Article 013413. https://doi.org/10.1103/PhysRevA.96.013413

• Journal Article Type: Article
• Acceptance Date: Jun 15, 2017
• Online Publication Date: Jul 17, 2017
• Publication Date: 2017-07
• Deposit Date: Jul 19, 2017
• Publicly Available Date: Jul 19, 2017
• Journal: Physical Review A
• Print ISSN: 2469-9926
• Electronic ISSN: 2469-9934
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 96
• Issue: 1
• Article Number: 013413
• DOI: https://doi.org/10.1103/PhysRevA.96.013413
• Public URL: https://nottingham-repository.worktribe.com/output/869886
• Publisher URL: https://link.aps.org/doi/10.1103/PhysRevA.96.013413
• Contract Date: Jul 19, 2017