Fragment emission anisotropy in the dissociative photoionization of O2 investigated by two-dimensional photoion spectroscopy

Yasumasa Hikosaka*, Tomohiro Aoto, Richard I. Hall, Kenji Ito

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The photoion yield from the photoionization of O2 has been measured in the 20.4-24.8 eV photon energy range as a function of both the incident photon energy and ion kinetic energy, at 0° and 90° with respect to the electric vector of the light. From the two-dimensional photoion spectra, photoion yield curves via the formation of O2+(B2Σg-) are extracted. Resonances due to the autoionization of the Rydberg states converging to O2+(c4Σu-) appear in both photoion yield curves measured at 0° and 90°, which indicates rotation in the O2+(B2Σg-) state prior to dissociation that smears the initial molecular orientation generated by photoabsorption. On the assumption that the lifetime of O2+(B2Σg-) is longer than the mean rotational period, photoion yield curves for parallel and perpendicular transitions are obtained. The two Rydberg series appear strongly in the parallel transition curve which implies that they have Σ symmetry. In the two-dimensional photoion spectra, a structure due to O autoionization following the dissociation of superexcited O2 states is identified. The photoion yield curves extracted for this process indicate the superexcited states responsible for the neutral dissociation and the symmetries of the states are determined from the observed fragment emission anisotropies.

Original languageEnglish
Pages (from-to)1423-1432
Number of pages10
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume36
Issue number7
DOIs
StatePublished - 2003/04/14

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics

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