Inverse photoemission and soft X-ray emission spectra of Al-Ni-Co decagonal single quasicyrstal

Inverse photoemission spectra (IPES) of a decagonal single quasicyrstal Al⁷²Ni₁₂Co₁₆ have been measured for various incident electron energies E_i together with its Al L₂₃ soft X-ray emission spectra (SXES). Both IPES and SXES show low intensity near the photon energy corresponding to the Fermi level, which is consistent with an opening of a pseudo-gap across the Fermi level. The IPES shows no strong resonance enhancement, suggesting apparently small density of the transition metal d states above the Fermi level. However, constant final state spectra of the inverse photoemission reveal faint humps around E_i = 62 and 76 eV, which might indicate resonances due to the Co and Ni 3d-derived states, respectively. A shoulder structure at the low photon energy side of the main band in the Al L_2,3 SXES becomes prominant for the lower incident electron energy and is tentatively ascribed to the Ni 3p emission band.