Electron-ion coincidence spectroscopy as a new tool for surface analysis - an application to the ice surface

Electron-ion coincidence (EICO) spectroscopy [K. Mass, M. Nagasono, S. Tanaka, M. Kamada, T. Urisu and Y. Murata: Rev. Sci, Inst 68 (1997) 1703] has recently been developed to investigate the process of ion desorption induced by the core level excitation. In the present study, we apply EICO spectroscopy to determine the O1s level of condensed H2O (ice) at 100 K. The kinetic energy of O1s photoelectrons which gives the highest coincidence yield of H+ desorption is shifted by about -0.7 eV compared to the O1s peak observed in the conventional core-level photoelectron spectroscopy. It is ascribed to a core-level shift in the O1s level from which hydrogen ions desorb. The results indicate the advantages and the possibilities of the EICO spectroscopy for surface analysis.