Vibration dependent branching and photoelectron angular distributions observed across the Cooper minimum region of bromobenzeneTools Powis, Ivan, Patanen, Minna, Antonsson, Egill, Nicolas, Christophe, Miron, Catalin and Holland, David M.P. (2017) Vibration dependent branching and photoelectron angular distributions observed across the Cooper minimum region of bromobenzene. Physical Review A, 96 (1). 013413. ISSN 1050-2947
Official URL: https://link.aps.org/doi/10.1103/PhysRevA.96.013413
AbstractVibrational 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.
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