Determination of the excited states of the electron centers and recording-readout processes in the X-ray storage material BaFBr

X射线存储材料BaFBr中电子中心激发态和记录读出过程的测定

• 批准号: 09450002
• 负责人: KONDO Yasuhiro
• 金额: $ 3.65万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09450002/
• 关键词: X-ray Imaging; Imaging Plate; Photo-Stimulated Luminescence; Phosphors; Luminescence; Electron trap centers; 2-D detectors; Detectior of InfraRed Light; 二次元検出器; 画像記録; X線; イオン結晶; 色中心; 発光分光; 励起状態; 赤外分光; 光物性

In the storage phosphor of the X-ray image material, the X-ray photons generate electrons and holes which are trapped at vacancies and Eu^<++> impurities in the micro crystals ofBaFBr : Eu^<++>(storage process) and photoexcitation of the trapped electron induces the recombination of the electrons and holes at Eu impurity, emitting the uv-luminescence. This uv-luminescence is recorded and is used to construct the X-ray image (readout process). Although the storage-readout mechanism described above has been proposed in the early stage of the invention of the imaging plate, the storage-readout process is still controversial at present. To establish the clear model for the mechanism, I tried to measured thermal stability of the excited state of the trapped electrons and also to clarify the recombination path of the electrons and holes. For this measurements, a system for the infrared luminescence was constructed. Results are summerized as follows.1) The temperature dependence of the luminescence intensity and its lifetime of the F center were measured and the thermal activation energy of the F centers in the excited state was obtained. This mechanism is identical to the that proposed by Takahashi.2) The F(F^-)-center luminescence in the IP was measured for the first time and it is also shown that F(Br^-) center does not emit any IR luminescence. These results shows that the electron center can migrate in the micro crystals in the IP and that the fading of the stored image might be induced by the migration of holes which are thermally activated in shallowly trapped hole centers.

在X射线成像材料的存储荧光粉中，X射线光子产生电子和空穴，这些电子和空穴被俘获在BaFBr：Eu^&lt；++&gt；微晶体中的空位和Eu^&lt；++&gt；(存储过程)，捕获的电子的光激发诱导电子和空穴在Eu杂质处复合，发出紫外光发光。这种紫外线发光被记录下来，并被用来构建X射线图像(读出过程)。尽管在成像板发明的早期阶段已经提出了上述存储-读出机制，但是存储-读出过程目前仍然存在争议。为了建立清晰的机理模型，我尝试测量了俘获电子激发态的热稳定性，并阐明了电子和空穴的复合路径。为此，建立了红外发光测量系统。1)测量了F心的发光强度及其寿命随温度的变化关系，得到了激发态F心的热激活能。这一机制与Takahashi提出的相同。2)首次测量了IP中的F(F^-)中心发光，并表明F(Br^-)中心不发射任何红外发光。这些结果表明，电子中心可以在激电层中的微晶体中迁移，存储图像的衰落可能是由于在浅陷阱空穴中心被热激活的空穴的迁移引起的。

项目成果

Yasuhiro Kondo, Kiyoshi Inoue, and Nobufumi Mori: "Luminuescence Study of F(Br-) and F(F-) Centres in BaFBr" Radiation Effects and Defects in Solids. 147(印刷中). (1999)

Yasuhiro Kondo、Kiyoshi Inoue 和 Nobufumi Mori：“BaFBr 中 F(Br-) 和 F(F-) 中心的发光研究”固体中的辐射效应和缺陷（1999 年）。

Yasuhiro Kondo, Kiyoshi Inoue, and Nobufumi Mori: "Luminescence Study of F (Br-) and F (F-) Centres in BaFBr" Radiation Effects and Defects in Solids. Vol.147 (in press). (1999)

Yasuhiro Kondo、Kiyoshi Inoue 和 Nobufumi Mori：“BaFBr 中 F (Br-) 和 F (F-) 中心的发光研究”固体中的辐射效应和缺陷。