Controlled Generation of Tm2+ Ions in Nanocrystalline BaFCl:Tm3+ by X-ray Irradiation

详细信息    查看全文

• 作者：Jun ZhangHans Riesen
• 刊名：Journal of Physical Chemistry A
• 出版年：2017
• 出版时间：February 2, 2017
• 年：2017
• 卷：121
• 期：4
• 页码：803-809
• 全文大小：449K
• ISSN：1520-5215

文摘

An investigation of the photoluminescence properties of divalent thulium generated by X-ray irradiation (X-irradiation) of nanocrystalline BaFCl:Tm³⁺ (250 ± 50 ppm) is reported. The X-irradiated samples show typical Tm²⁺ f–f luminescence with an excited state lifetime τ = 0.98 ± 0.05 ms in the near-infrared (∼1140 nm), but no d–f luminescence is observed for the BaFCl host material within the visible range. The Tm²⁺ ions are relatively stable under dim room light but are photoionized rapidly by sunlight or by fluorescent tube lighting. To study the X-ray storage mechanism, photoluminescence intensities of both Tm³⁺ and Tm²⁺ transitions were measured, and the reverse photoionization of Tm²⁺ was investigated as a function of the laser power density and the initial radiation dose. The photoionization data was then modeled by employing equations based on dispersive first order kinetics using a standard Γ distribution function for the separation between the reduced thulium ions and the hole traps. In accord with previous reports, the hole traps are most likely oxide impurities such as O^2–, and the average of the separation is found to be ∼6–7 Å, i.e., a few interionic spacings.