Resonant inelastic x-ray scattering and UV–VUV luminescence at the Be 1s edge in BeO

Abstract

We carried out a combined study of UV-VUV luminescence and resonant x-ray emission from BeO single crystals with incident photon energies in the vicinity of the Be 1s absorption edge. The x-ray emission spectra show that at the Be 1s photoabsorption edge the lattice relaxation processes in the excitation site take place already on the timescale of the radiative decay of the core excitation. Comparison of the x-ray emission and the luminescence spectra indicates that the maximum energy loss of the process of lattice relaxation during the decay of inner-shell holes is similar to the loss that occurs in the self-trapping process of valence excitons. The possible decay channels of core excitations have been discussed and the mechanism for the creation of 5.2 eV luminescence at the photoabsorption resonances has been suggested.

Ultrafast electronic processes in an insulator: The Be and O sites in BeO

“…The sharp line (green curve) at the energy of 119.3 eV is due to elastic resonant scattering and indicates the energy resolution of the whole apparatus. In agreement with a pioneering x-ray investigation of BeO, 47 we find a bi-modal decay structure due to energetic relaxation (involving electron-phonon coupling) of the corehole exciton. This bi-modal peak structure is indicated also by the two blue arrows in Fig.…”

“…1 is broader than expected beforehand. Furthermore, these x-ray investigations 46,47 indicate that exciton population and relaxed exciton decay are strongly suppressed by non-resonant and by nonperturbative interactions (interactions of highly charged ions lead to elevated temperatures of the electron systems and of the lattice). Thus, exciton population might have some small influence on the spectra for Ar 7+ ions in Fig.…”