Decay process of Li 1s core exciton in lithium halides studied by photoelectron spectroscopy.

Abstract

The decay process of the Li 1s core exciton was investigated by measuring the photoelectron spectra of LiCl and LiBr. It was observed that the valence-band spectrum as well as the Auger peak is enhanced at photon energies close to the excitation energy of the Li 1s core exciton. To explain these phenomena the following two processes were proposed: A Li 1s core hole and an excited electron which form the Li 1s core exciton may recombine directly with energy transferred to a valence electron. In this case, the valence-band photoelectron spectrum is resonantly enhanced at the photon energy close to the excitation energy of the core exciton, since the final state of this process is the same as that of the direct photoexcitation from the valence band. In the second process, the Li 1s core hole forming a core exciton recombines with a valence electron transferring energy to another valence electron which is excited to the continuum state. This process results in an enhancement of the Auger-electron peak. The decay probability of the Li 1s core exciton through these two processes was estimated from the photoelectron spectra and the Li K absorption spectra. It was found that the latter process is a predominant decay process in lithium halides.