High-resolution spectroscopy in the far ultraviolet

Thermoreflectance (TR) measurements have extended to the far ultraviolet the high-resolution modulation techniques well established at lower energies. The TR spectrum of gold showed for the first time several new features up to 36 eV. Their interpretation is reanalysed also in view of recent CIS photoemission measurements. The TR spectra of the Rb+4 p core excitons in Rb halides allowed us to resolve at 200 K some structures previously observed only at 8 K, enabling us to determine their temperature dependence. The exciton-phonon interaction is suggested to be responsible for the partial failure of the ligand field model for core excitons. The ionization continuum threshold of the Rb+4 p states is also determined. Finally, TR experiments allowed us to discriminate between different interpretations suggested for the strong electron energy loss peak at the end of the valence band excitations of alkali halides. © 1977 Società Italiana di Fisica.