S. Tanaka, K. Mase, M Nagasono, S. Nagaoka, M. Kamada, E. Ikenaga, T. Sekitani,
and K. Tanaka
[Jpn. J. Appl. Phys., 39, 4489-4492 (2000)]
Electron-ion coincidence (EICO) Spectroscopy [K. Mase, 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 -0.7eV 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.
K. Mase, S. Tanaka, S. Nagaoka, and T. Urisu
[Surf. Sci., 451, 143-152 (2000)]
The recent investigations of ion desorption induced by core-electron transitions using electron-ion coincidence (EICO) spectroscopy are described. In a study of CF3CH(OH)CH3 chemisorbed on a Si(100) surface using photoelectron photoion coincidence (PEPICO) spectroscopy, excitation site-specific ion desorption is directly verified, that is, F+ desorption is predominant for C 1s photoionization at the-CF3 site, while H+ desorption is predominantly induced by C 1s photoionization at the -CH3 site. A study of condensed H2O using Auger electron photoion coincidence (AEPICO) spectroscopy showed that H+ desorption is stimulated by O KVV Auger processes leaving two-hole states. The H+ desorption probability is found to depend on the bonding character of the orbitals where holes are created and on the eVective hole-hole Coulomb repulsion. AEPICO investigations of H+ desorption induced by resonant core-electron excitations of condensed H2O clearly showed that one-electron-one-core hole or oneelectron -two-valence hole states are responsible for the H+ desorption mechanism. These investigations demonstrate that EICO spectroscopy combined with synchrotron radiation is a novel and powerful tool for the study of ion desorption induced by core-electron excitations. Furthermore, a comparison of PEPICO and photoelectron spectra showed that the surface core-level shift of condensed H2O is 0.7 eV. This study shows that PEPICO spectroscopy is also promising as a method to investigate the electronic structure of the specific sites responsible for ion desorption.
S. Tanaka, K. Mase, M Nagasono, S. Nagaoka, and M. Kamada
[Surf. Sci., 451, 182-187 (2000)]
Photo-stimulated desorption from the TiO2(110) surface was investigated by using electron-ion coincidence spectroscopy and synchrotron radiation. The desorption of O+ ions was observed to be coincident with the emission of photoelectrons from the O 1s, Ti 2s, Ti 2p, Ti 3s and Ti 3p levels, and their satellite peaks due to the shake-up excitation. However, no ion desorption was observed in coincidence with the O 2s or valence photoelectrons. The O+ peak intensities in the coincidence spectra are analyzed, and the result is unexpected from a simple expansion of the Knotek-Feibelman model. The shake-up excitation of O 1s levels yields O+ desorption more efficiently than does the O 1s single-electron excitation.
間瀬一彦
[Kanae、13、 18-29 (2000)]
CMA（円筒鏡面型電子エネルギー分析器）はオージェ電子分光や電子−イオン・コインシデンス分光など、 さまざまな研究に使用されている有用な機器である。本稿では超高真空仕様CMA製作技術を初心者向けに具体的に解説する。
間瀬一彦
[化学と工業、53、111-116 (2000)]
表面分子の内殻電子をイオン化するとオージェ過程によって２正孔状態が生成し、イオンが脱離する。 オージェ電子−光イオン・コインシデンス分光法によって、オージェ終状態を選別してイオン脱離収量を測定できるようになり、 オージェ過程に由来する様々なイオン脱離過程が解明された。また、イオン脱離確率を支配する因子などに関して新しい知見が 得られた。オージェ電子−光イオン・コインシデンス分光法によって内殻電子励起に由来する表面ダイナミックスという新しい 化学のフロンティアが開かれようとしている。