关于不同波长的LED的吸收的处理，参考：
- jieqi_20221023.pptx，在文件夹【E:\phd\CaF2\CaF2文章\2022汇报\第3次汇报】
- 在文件夹【E:\phd\CaF2\CaF2文章\2022汇报\第3次汇报\图-3】下的PPT
- 蓝光功率44.94 mW/cm2，绿光功率26.62 mW/cm2，红光28.7324 mW/cm2
为什么Eu2+的发射峰有个尾巴？
- Modification of luminescence spectra of CaF2: Eu2+
- Dose dependence of x-ray luminescence from CaF2:Eu2+ , Mn2+ phosphors
- Sensitization of Pr3+ ions by Eu2+ ions in CaF2 thin films deposited by evaporation
另一个defect和Sm3+的redox
- Dalton Trans., 2021, 50, 16205-16213
- Oxygen impurities (O2− ions) most likely act as hole traps.58,59 Such impurities may stabilize Sm3+ ions if they are in very close proximity and consequently
- the electrons may be initially trapped directly by an anion vacancy such as the intrinsic F-center in the CaF2 host lattice.
- Radiation Effects in CaF2:Sm
- 认为氧不是
- This material now has a pale green color which is stable to high-temperature heating in an oxygen-free atmosphere.
- Optical absorption spectra of X-ray irradiated alkaline earth fluoride crystals doped with divalent rare-earth ions studied by thermal bleaching
- Also under X-ray irradiation at room temperature absorption bands related to the hole F3− and (F2−)ii centers were found in these crystals.
photo-bleaching:
- Evidence for electron trapping by Sm dimer and trimer centers in Sm doped CaF2
- 合成的CaF2:Sm中的初始状态，大部分Sm是二价，但是也有少量的三价。
- 690 nm染料激光器，或者Nd:YAG的倍频波长532 nm的辐照，都可以是的使得原来dark green的样品变为light green.
- This color change is reversible upon irradiation with light around 360 nm. 也就是重新着色过程
- Apparently these photochromic properties do not change from liquid nitrogen up to room temperature. Neither the bleached, nor the darkened samples show any color change after storage for weeks at room temperature.
- To bleach the sample, it was irradiated for 5 min at 10 K with the unfocused dye laser beam at 610 nm with an average power of 100 mW. The use of a pulsed laser for this experiment is justified due to the two-photon nature of the photoionization process 此处来自[Electron trapping by self-trapped hole pairs and small rare-earth clusters in Sm-doped CaF2] 同一作者，样品都是初始状态下有少量的Sm2+
- Photo bleaching in Sm2+ selectively doped epitaxial CaF2 films
- 用的是HeNe 激光器，波长632.8 nm。
- Fig. 3 shows the surprising experimental result: the bleaching rate depends linearly on the pump power. A two-step ionization process is un- der certain circumstances compatible with a quasi- linear power dependence if the electrons are excited from the Si valence band back into the conduction band in an one-step process, but direct proof is missing. Experiments, including photoconductivity measurements, are under way to investigate this energy transfer process in more detail.
- Photoionization hole burning and nonlinear Zeeman effect in CaF2:Sm2+
- CaF2 doped with europium and samarium has long been known to exhibit photochromism under broad UV irradiations In that system, the Eu2+ ion was photo-oxidized, and the role of Sm3+ was to act as an electron acceptor. In our experiments, we selectively bleach the Sm2+ absorption in the lowest excited state and find that this occurs both in the presence of europium codoping and in the absence of any codopant. Photoconductivity thresholds for several divalent rare-earth ions in CaF2 have been measured by Pedrini et al.12 with the aim of locating the levels of the rareearth ion with respect to the conduction band of CaF2. They find ionization thresholds of 2.75 eV for Tm2+, 1.75 eV for Ho2+, and 1.76 eV for Dy 2 +. The threshold for Sm2+ has not yet been reported. We find that repeated and prolonged hole burning eventually leads to a bleaching of the green coloration, showing that Sm2+ has been oxidized. Further evidence that hole burning occurs by photoionization is provided by measurements in the doubly doped samarium/europium crystals where excitation of Sm2+ at 690.2 nm leads to blue fluorescence from Eu 2+, i.e., the electron that leaves Sm2+ is trapped at Eu3+, yielding Eu2+ in an excited state.
- CaF2 doped with europium and samarium has long been known to exhibit photochromism under broad UV irradiations In that system, the Eu2+ ion was photo-oxidized, and the role of Sm3+ was to act as an electron acceptor. In our experiments, we selectively bleach the Sm2+ absorption in the lowest excited state and find that this occurs both in the presence of europium codoping and in the absence of any codopant. Photoconductivity thresholds for several divalent rare-earth ions in CaF2 have been measured by Pedrini et al.12 with the aim of locating the levels of the rareearth ion with respect to the conduction band of CaF2. They find ionization thresholds of 2.75 eV for Tm2+, 1.75 eV for Ho2+, and 1.76 eV for Dy 2 +. The threshold for Sm2+ has not yet been reported. We find that repeated and prolonged hole burning eventually leads to a bleaching of the green coloration, showing that Sm2+ has been oxidized. Further evidence that hole burning occurs by photoionization is provided by measurements in the doubly doped samarium/europium crystals where excitation of Sm2+ at 690.2 nm leads to blue fluorescence from Eu 2+, i.e., the electron that leaves Sm2+ is trapped at Eu3+, yielding Eu2+ in an excited state.
- Luminescence and photoionization of X-ray generated Sm2+ in coprecipitated CaF2 nanocrystals
32 mGy X-irradiated nanocrystalline CaF2:Sm3+ as a function of photobleaching time with 25 mW of 425 nm laser diode light.
thermal bleaching：
- 我的实验条件：气氛，都是0.12 的纯氮气，开冷却水 650， 600，500，525，500，都是升温2个小时，保温5分钟； 470，440度，一个半小时升温，保温5分钟； 400度，升温一个小时，保温5分钟； 350度，升温一个小时，保温5分钟； 300度，升温一个小时，保温5分钟； 250度，升温45分钟，保温5分钟； 200度，升温30分钟，保温5分钟； 150度，升温22分钟，保温分钟； 100度，升温15分钟，保温分钟； 485度，升温1小时45分钟，保温5分钟
- 文献的实验条件：
不同波长响应的讨论包括：
- 已经报道的Sm2+ bleaching的例子，不一定包含另一个掺杂例子，不过限于CaF2基质；