Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation
Vernadsky National Library of Ukraine
Переглянути архів Інформація| Поле | Співвідношення | |
| Title |
Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation
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| Creator |
Kazuhiko Mase
Mitsuru Nagasono Shin-ichiro Tanaka Tetsuji Sekitani Shin-ichi Nagaoka |
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| Subject |
Electronically Induced Phenomena: Low Temperature Aspects
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| Description |
This article reviews our recent work on photo-stimulated ion desorption (PSID) from molecules condensed at low temperature. We have used electron-ion coincidence (EICO) spectroscopy combined with synchrotron radiation. The history and present status of the EICO apparatus is described, as well as our recent investigations of condensed H₂O, NH₃, CH₃CN, and CF₃CH₃. Auger electron photoion coincidence (AEPICO) spectra of condensed H₂O at the O:1s ionization showed that H⁺ desorption was stimulated by O:KVV Auger processes leading to two - hole states (normal- Auger stimulated ion desorption (ASID) mechanism). The driving forces for H⁺ desorption were attributed to the electron missing in the O - H bonding orbitals and the effective hole-hole Coulomb repulsion. The normal ASID mechanism was also demonstrated for condensed NH₃. The H⁺ desorption at the 4a₁ ← O(N):1s resonance of both condensed H₂O and condensed NH₃ was found to be greatly enhanced. Based on the AEPICO spectra the following four-step mechanism was proposed: (1) the 4a₁ ← 1s transition, (2) extension of the HO - H (H₂N - H) distance within the lifetime of the (1s)⁻¹(4a1)¹ state, (3) spectator Auger transitions leading to (valence)⁻²(4a₁)¹ states, and (4) H⁺ desorption. The enhancement of the H⁺ desorption yield was attributed to the repulsive potential surface of the (1s) - 1(4a₁)¹ state. At the 3p ← O:1s resonance of condensed H₂O, on the other hand, the H⁺ yield was found to be decreased. The AEPICO spectra showed that the H⁺ desorption was stimulated by spectator Auger transitions leading to (valence)⁻²(3p)¹ states. The decrease in the H⁺ yield was attributed to a reduction in the effective hole-hole Coulomb repulsion due to shielding by the 3p electron. Photoelectron photoion coincidence (PEPICO) spectra of condensed H₂O showed that the core level of the surface H₂O responsible for the H⁺ desorption was shifted by 0.7 eV from that of the bulk H₂O. The H⁺ desorption from condensed CH₃CN was also investigated. In a study of condensed CF₃CH₃ using PEPICO spectroscopy, site-specific ion desorption was directly verified; that is, H⁺ and CH₃⁺ desorption was predominant for the C:1s photoionization at the -CH₃ site, while C₂Hn⁺, CFCHm⁺, and CF₃⁺ desorption was predominantly induced by the C:1s photoionization at the -CF₃ site. These investigations demonstrate that EICO spectroscopy combined with synchrotron radiation is a powerful tool for studying PSID of molecules condensed at low temperature.
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| Date |
2018-01-14T09:15:17Z
2018-01-14T09:15:17Z 2003 |
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| Type |
Article
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| Identifier |
Ion desorption from molecules condensed at low temperature: A study with electron-ion coincidence spectroscopy combined with synchrotron radiation / Kazuhiko Mase, Mitsuru Nagasono, Shin-ichiro Tanaka, Tetsuji Sekitani, Shin-ichi Nagaoka // Физика низких температур. — 2003. — Т. 29, № 3. — С. 321-341. — Бібліогр.: 106 назв. — англ.
0132-6414 PACS: 79.20.La, 07.81.+a http://dspace.nbuv.gov.ua/handle/123456789/128820 |
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| Language |
en
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| Relation |
Физика низких температур
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| Publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
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