High-Resolution He i and He ii Photoelectron Spectra of Xenon Difluoride

Abstract

The vertical I.P.'s of the first eight ionizations in the XeF2 molecule have been determined, and they compare favorably with the results of Gaussian‐type orbital calculations. The first two ionic states of XeF2 are the 2Π3/2 (12.42 eV) and 2Π1/2 (12.89 eV) spin–orbit components formed by ionization from the highest‐filled π orbital (5π u ) . As judged by the vibronic structure of the transitions, the two upper states are linear, with Xe–F distances very much like those of the ground state. The fifth (15.60 eV) and sixth (16.00 eV) I.P.'s similarly involve the ejection of an electron from the 4π u orbitals, and thus they are separated by the action of spin–orbit coupling. Substitution of He ii α excitation (40.82 eV) for the He i α excitation (21.21 eV) results in both the additional ionization of electrons from the 9σ g molecular orbital (22.5 eV), and a drastic change in the relative intensities of certain peaks in the lower I.P. region. Rydberg bands in the optical spectrum of XeF2 can be correlated with those of the photoelectron spectrum, yielding assignments in essential agreement with those given by earlier workers. The work with the He ii resonance line is described in some detail because a description of its use in photoelectron spectroscopy has not previously appeared in the literature.