Note: XAS is a complementary technique with XPS to study a chemical state of elements in materials. XPS probes occupied-state electron densities excited to unoccupied states, while XAS probes unoccupied-state electron densities excited from occupied states. Both techniques are based on the free-electron-like unoccupied states to probe the occupied state electron densities. However, XPS directly probes electron energies at a fixed photon energy, so the charging and surface effects cannot be avoidable. XAS has an advantage to measure the insulating samples if the unoccupied states are almost equivalent in materials to be compared. Soft x-rays do not penetrate the beryllium window for a hard x-ray beamline, so UHV conditions at the analysis system are nessesary to measure absorption spectra involving core levels in the soft x-ray energy range such as C, N, and O K edges. Soft x-ray absorption in materials is mainly governed by Auger electron emissions resulting from a small probability on fluorescence process to release the absorbed photon energy. Therefore, the workfunction difference formed at surfaces in materials are negligible. In the "soft" XAS measurement in BL3.2a, the photon flux, energy resolving power, and polarization and surface sensitivities are much higher than those obtained in BL8. However, the soft XAS measurement is performed only in the electron yield mode, because the transmission of samples and its holder materials are quite low.

 

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Some results on the commissioning of the undulator beamline 3.2 by gas-phase photoionization spectroscopy are shown.

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