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Electron beam induced effects on oxygen exposed Beryllium
A451 Shigeru SHINDO
Department of Physics, Tokyo Gakugei University, Koganei, Tokyo 184, Japan Received 25 March 1987; accepted for publication 30 April 1987 A quantum mechanical theory of the positronium formation at surfaces is presented. Not only the formation process of positronium but also the dissociation process of it is necessary to explain experiments. Second-order calculation is sufficient for the wide electron band, but numerical calculation of the original integro-differential equation is necessary for the narrow band case.
996
Surface Science 189/190 (1987) 996-1002 North-Holland, Amsterdam
ENERGY D I S T R I B U T I O N OF S L O W P O S I T R O N S FROM
METAL
Masahiko
KATO
RE-EMrI'TED
SURFACES *
Department of Physics, Waseda University, Shinjuku, Tokyo, Japan and Akira ISHII
**
Institute of Material Science, University of Tsukuba Sakura-mura, Ibaraki 305, Japan Received 24 March 1987; accepted for publication 14 May 1987 The electron-hole pair excitation by the positrons which are spontaneously re-emitted from metal surfaces is studied. When the positron is inside the metal, the positron is thermalized by the interaction caused by the target metal. However, when the positron is emitted outside, tiffs interaction quickly switches off. Thus, employing the "sudden" approximation, we study the possibility of the infrared divergence of electron-hole pairs. The theory shows that if both positron states inside and outside the metal are not localized, the positrons are essentially free from electronic excitations.
Surface Science 189/190 (1987) 1003-1008 North-Holland, Amsterdam
1003
ELECTRON BEAM INDUCED EFFECTS ON OXYGEN EXPOSED BERYLLIUM D.L. SEYMOUR
* and E.B. PATI'INSON
Department of Physics, University of Keele, Keele, Staffs, UK Received 27 March 1987; accepted for publication 15 April 1987 Electron beam induced effects are known to be important on some oxygen exposed surfaces. We present results from a number of experiments which have been performed on polycrystalline beryllium exposed to low levels of oxygen pressure. Beryllium and oxygen Auger spectra have been recorded as a function of both oxygen exposure and electron dose, for doses up to 16 C / c m 2. The cross section for the electron stimulated desorption of oxygen from beryllium, which has not previously been determined was found to be of the order of 1 × 10 -21 cm 2. It is believed that the resorption occurs simply as a result of electronic excitations of the valence band and shallow core levels.
Department of Physics, Tokyo Gakugei University, Koganei, Tokyo 184, Japan Received 25 March 1987; accepted for publication 30 April 1987 A quantum mechanical theory of the positronium formation at surfaces is presented. Not only the formation process of positronium but also the dissociation process of it is necessary to explain experiments. Second-order calculation is sufficient for the wide electron band, but numerical calculation of the original integro-differential equation is necessary for the narrow band case.
996
Surface Science 189/190 (1987) 996-1002 North-Holland, Amsterdam
ENERGY D I S T R I B U T I O N OF S L O W P O S I T R O N S FROM
METAL
Masahiko
KATO
RE-EMrI'TED
SURFACES *
Department of Physics, Waseda University, Shinjuku, Tokyo, Japan and Akira ISHII
**
Institute of Material Science, University of Tsukuba Sakura-mura, Ibaraki 305, Japan Received 24 March 1987; accepted for publication 14 May 1987 The electron-hole pair excitation by the positrons which are spontaneously re-emitted from metal surfaces is studied. When the positron is inside the metal, the positron is thermalized by the interaction caused by the target metal. However, when the positron is emitted outside, tiffs interaction quickly switches off. Thus, employing the "sudden" approximation, we study the possibility of the infrared divergence of electron-hole pairs. The theory shows that if both positron states inside and outside the metal are not localized, the positrons are essentially free from electronic excitations.
Surface Science 189/190 (1987) 1003-1008 North-Holland, Amsterdam
1003
ELECTRON BEAM INDUCED EFFECTS ON OXYGEN EXPOSED BERYLLIUM D.L. SEYMOUR
* and E.B. PATI'INSON
Department of Physics, University of Keele, Keele, Staffs, UK Received 27 March 1987; accepted for publication 15 April 1987 Electron beam induced effects are known to be important on some oxygen exposed surfaces. We present results from a number of experiments which have been performed on polycrystalline beryllium exposed to low levels of oxygen pressure. Beryllium and oxygen Auger spectra have been recorded as a function of both oxygen exposure and electron dose, for doses up to 16 C / c m 2. The cross section for the electron stimulated desorption of oxygen from beryllium, which has not previously been determined was found to be of the order of 1 × 10 -21 cm 2. It is believed that the resorption occurs simply as a result of electronic excitations of the valence band and shallow core levels.