Introducing the Community Guide's Reviews of Evidence on Interventions to Increase Screening for Breast, Cervical, and Colorectal Cancers

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• 作者：Rosalind A. Breslow ; Barbara K. Rimer ; Roy C. Baron ; Ralph J. Coates ; Jon Kerner ; Katherine M. Wilson ; Nancy C. Lee ; Patricia Dolan Mullen ; Steven S. Coughlin ; Peter A. Briss
• 关键词：Silica glass ; Oxygen vacancy ; EPR
• 刊名：American Journal of Preventive Medicine
• 出版年：2008
• 期刊代码：8_07493797
• 类别：med
• 出版时间：July 2008
• 卷：35
• 期：1, Supplement 1
• 页码：S14-S20
• 文件大小：159 K

摘要

Spectroscopic properties of hydrogen atom trapped in an oxygen vacancy in SiO₂ glass were studied. Samples were loaded with D₂ and H₂ gases to convert O vacancies to pairs of Si–D and Si–H groups, and subsequently irradiated by F₂ laser in order to destroy some of these groups. Electron paramagnetic resonance, infrared absorption and visible/UV absorption spectra were measured. Proton hyperfine doublet with splitting of 1.05 mT was found in all H₂-treated/irradiated samples. UV-bleaching treatment showed that this signal is independent of the other, well-known hydrogen-related signals in silica. The size of the hyperfine splitting corresponds to twice the ¹H nuclear Zeeman splitting in applied magnetic field. The observed 1.05 mT doublet is tentatively attributed to the forbidden nuclear spin-flip transitions of proton trapped in an oxygen vacancy in silica. The allowed EPR transitions of this center are not resolved, possibly reflecting a variation in Si H distance in oxygen vacancy with a trapped H atom.