Thermomodulation spectra of high-energy interband transitions in Cu, Pd, Ag, Pt, and Au

Thermotransmission and thermoreflectance spectra were obtained for Cu, Pd, Ag, Pt, and Au in the 10-30 eV spectral region. Structures due to transitions from the Fermi level to high-density bands 15 eV above the Fermi level were identified in Pt. All metals showed structures arising from interband transitions between the $d$ bands and the same flat bands, 15-20 eV above the Fermi energy. Attempts to fit to interband critical points in Au revealed over 40 possible critical points in the region of these structures, most of them near the Brillouin-zone centers. Systematic trends in the series of metals make the qualitative identification of the structures more secure, and no energy shifts of calculated energy bands are required. The observed widths of structures are sometimes much narrower than the widths of free-electron-like bands at comparable energies.