The effect of autoionization on the HBr+ X 2Π3/2,1/2 state photoelectron angular distributions

• Published in: Chemical physics 2020-11, Vol.539, p.110961, Article 110961
• Main Authors: Hrodmarsson, H.R., Gans, B., Boyé-Péronne, S., Garcia, G.A., Nahon, L., Pratt, S.T., Holland, D.M.P.
• Format: Article
• Language: English
• Subjects: Autoionizing Rydberg states; Chemical Physics; Hydrogen bromide; Photoelectron angular distributions; Physics; Threshold photoelectron spectrum
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2020.110961

[Display omitted] •Photoelectron angular distributions of the HBr+ X state have been measured.•Photoelectron anisotropy parameters affected by autoionizing Rydberg states.•X state threshold electron spectrum exhibits partially resolved rotational structure.•Rydberg states observed in ion yield. A double-imaging photoelectron-photoion spectrometer and synchrotron radiation have been used to measure the HBr+ X 2Π3/2v+ = 0, 1, 2 and the 2Π1/2v+ = 0 state photoelectron angular distributions, as characterized by the anisotropy parameter β, the total ion yield, and the threshold photoelectron spectrum. Particular attention has been focussed on the photon energy range between the 2Π3/2 and the 2Π1/2 spin–orbit components of the ground ionic state. This region encompasses Rydberg states, belonging to series converging onto the upper 2Π1/2 ionization limit, which may decay by autoionization into the 2Π3/2 ionization continuum. A detailed study has been performed on the effects of autoionization on the 2Π3/2v+ = 0 state photoelectron angular distributions. The observed energy dependent variations in the β-values exhibit a regular pattern that correlates with excitation into members of a very broad d-type Rydberg series. Additional rapid variations in the β-parameters, which occur over a narrow energy range, appear to coincide with sharp autoionizing Rydberg states belonging to s, p and d series. The present experimental results for the HBr+ X 2Π3/2v+ = 0 state photoelectron anisotropy parameter are compared to previously reported theoretical predictions and to earlier studies of the Kr+ 4p5 2P3/2 state β-parameter. The threshold photoelectron spectrum of the X 2Π3/2v+ = 0 band exhibits partially resolved rotational structure. A simulation of this structure yields an ionization threshold of 11.6673 ± 0.0010 eV, which is consistent with previous measurements.