LiBaF3:Eu2+真空紫外光谱研究

在室温下，二价稀土离了 杂的LiBaF3:Eu^2 粉末样品中，Eu^2 的发射呈现双峰结构，有一峰值波长约为410nm的宽峰，对应于Eu^2 的5d-4f跃迁，以及另一峰值波长约为360nm的窄峰，对应于Eu^2 的4f-4f跃迁。在50－400nm波长范围，测量了样品的反射光谱，并利用Kramers-Kroenig关系，计算了吸收光谱。从吸收光谱中，可以看到在102nm处有明显的吸收边，得到LiBaF3材料的禁带宽度Eg约为12.1eV。在高能端有53.4,59.4,65.3,69.2和76.5nm的吸收峰，它们对应于Ba^2 的5p电子和F的2p电子芯能级之间的跃迁，在低能量的183.4nm处，有很明显的吸收峰，推测这对应于本征缺陷的吸收。更低能量的吸收峰，则对应于禁带中的一些杂质能级，在未经紫外光或X射线辐照之前，用长波长（＞450nm）光激发LiBaF3:Eu^2 粉末样品，可以观测到Eu^2 离子的360nm和410m发光，亦表现出光激励发光特性。

Vacuum Ultra-violet Spectra of LiBaF3:Eu2+

At room temperature, there are two emission peaks in the luminescence spectrum of LiBaF3: Eu2+ powder sample. One is a broad band peaked at 410nm, and the other one is a narrow band peaked at 360nm, corresponding to 5d-4f and 4f-4f transitions of Eu2+, respectively. Furthermore, taking the reflection spectrum of Au thin film as reference, the reflection spectra of LiBaF3: Eu2+ sample are measured in the range of 50-400nm at U10B station of the National Synchrotron Radiation Laboratory (NSRL). The absorption spectra are calculated from the reflection spectrum by using the Kramers-Kronig relation. It is found that the energy gap Eg of this material is about 12.1eV. We believe that in the absorption spectra of LiBaF3:Eu2+, the 53.4, 59.4, 65.3, 69.2 and 76.5nm sub-bands correspond to transitions between core levels of Ba2+ 5p and F-2p electrons, respectively. Then the 183.4nm sub-band is attributed to the intrinsic defects absorption.On the other hand, without the pre-irradiation, one can observe the luminescence of LiBaF3: Eu2+ powder sample under the excitation of wavelength longer than 450nm. It means that the LiBaF3:Eu2+ sample has the photo-stimulated character.