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Photodissociation of polycrystalline and amorphous water ice films at 157 and 193 nm

Photodissociation of polycrystalline and amorphous water ice films at 157 and 193 nm. A. Yabushita, D. Kanda, N. Kawanaka, and M. Kawasaki. Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan. M. N. R. Ashfold. Reviewed by A. Nagaoka, January 16, 2007.

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Photodissociation of polycrystalline and amorphous water ice films at 157 and 193 nm

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  1. Photodissociation of polycrystalline and amorphous water ice films at 157 and 193 nm A. Yabushita, D. Kanda, N. Kawanaka, and M. Kawasaki Department of Molecular Engineering, Kyoto University, Kyoto 615-8510, Japan M. N. R. Ashfold Reviewed by A. Nagaoka, January 16, 2007 School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom THE JOURNAL OF CHEMICAL PHYSICS 125, 133406 (2006)

  2. 水蒸気の紫外線分解 H2Ovapor + hv → H + OH 高度80 km付近には氷微粒子(夜光雲)が形成される 氷の紫外線分解 H2Oice + hv → H + OH HOxサイクルによるオゾン(O3)分解 H + O2 → HO2 HO2 + O3 → OH + 2O2 OH + O3 → H + 2O2

  3. 背景 大気の鉛直構造 オゾン濃度 オゾン濃度が中間圏上層部で極小となる原因は？

  4. 128 nm 207 nm Yabushita 2006

  5. Yabushita 2006

  6. 目的 氷の紫外線(157, 193 nm)解離によるH原子生成過程を実験的に調べる 光解離生成物(H原子)の運動エネルギーを測定 氷の構造依存性

  7. Experimental setup Au-coated sapphire substrate 100 K (amorphous ice) 130 K (crytalline ice) 色素レーザー （Laser for REMPI: 243 nm） 飛行時間型 質量分析計 ice エキシマーレーザー H2O Vacuum chamber (base pressure: 10-8 Torr) （Laser for photodissociation: 157 and 193 nm）

  8. Experimental procedures ① ② ③ Flight length= 3mm H H2O 100 K Substarte (100 K for amorphous 130 K for crytalline) 157 or 193 nm ④ ⑤ ⑥ acceleration → detection by mcp 243 nm H+ (REMPI)

  9. Resonance-Enhanced Multiphoton Ionization (REMPI) （共鳴多光子イオン化法） H + hn → H+ + e イオン化準位 243.1 nm １光子吸収 共鳴準位 (2+1) REMPI 243.1 nm ２光子吸収 243.1 nm 基底準位

  10. TOF measurement （Crystalline ice, Tice=100K） Translational temperature of H (contribution) TA=4750±250 K (41%) (7.9eV) TB= 625±25 K (44%) TC= 110±10 K (15%) TA’=2400±100 K (100%) (6.4eV)

  11. TOF measurement （Amorphous ice, Tice=100K） Translational temperature of H (contribution) TA=4750±250 K ( 3%) TB= 625±25 K ( 5%) TC= 110±10 K (92%) TA’=2400±100 K (15%) TC= 110±10 K (85%)

  12. Origin of the components Surface → thermalize Surface Bulk (氷内部) Amorphous ice

  13. Yabushita 2006

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