BaF_2：Ce，La，Eu晶体的光谱性质

Spectra Properties of BaF_2:Ce, La, Eu Crystals

用脱氧剂非真空环境下Ｓｔｏｃｋｂａｒｇｅｒ方法生长未掺和掺铈、镧、铕的浓度范围在１００～５０００ｐｐｍｗｔ的ＢａＦ２晶体．脱氧剂生长方法具有设备简单，不用抽真空和批量生产透明大单晶的特点．测量了这些晶体在室温下透射、激发，以及Ｘ射线和紫外光激发的发射光谱．由Ｘ射线激发，掺杂１０００ｐｐｍ的Ｃｅ样品具有峰值在３０７ｎｍ和３２１ｎｍ二个发射带，被归为放没有其它邻近铈离子条件下Ｃｅ（３＋）的５ｄ－４ｆ跃迁．对于掺杂５０００ｐｐｍ的Ｃｅ晶体，新的发射带出现在峰值为３４０ｎｍ的３２６～３７５ｎｍ范围．新的发射带仍是Ｃｅ（３＋）离子５ｄ－４ｆ跃迁引起的，与其它邻近Ｃｅ离子相互作用，使５ｄ能级朝着较低能量迁移．１０００ｐｐｍ的样品具有最大发光强度，以及闪烁波长＞３００ｎｍ具有封闭电子壳层外加阳离子Ｌａ（３＋）很少影响心一价带跃迁（ＣＶＴ），但是降低慢分量（激子）发射强度．ＢａＦ２：１ｗｔ％Ｌａ样品的快／慢分量比＞纯的样品的快／慢分量比．镧杂质抑制慢分量，并保持未掺ＢａＦ２辐照硬度．Ｘ射线激发ＢａＦ２：１００ｐｐｍＥｕ发射光谱呈现二个部分：相对强的３００ｎｍ本征慢分量发光，以及～４３０和５９０ｎｍＥｕ（２＋）离子二个特征弱?

BaF2 undoped and doped with cerium, lanthanum and europium in the 100￣5000ppm wt range were grown not in vacuum by the stockbarger process used with deoxidant. The growth method with deoxidant possesses the features. as follows: crystal growth equipment is simple and growth enviroment is not in vacuum, this method can realize batch process of large single crystal with transparency. We measured the transmissiom, excitation and emission spectra excited by X-ray and UV light for these crystals at room temperature. The 1000ppm Ce doped sample 11as two emission bands excited by X-ray peaked at 307urn and 321nm which are attributed to 5d-4f transitions in Ce(3+) ions with no other Ce ions in their vicinity. New emissions for 5000ppm sample appear in the 326nm to 375urn region peaked at 340urn which caused by same transitions with 5d levels shifted towards lower energy due to interactions with other near Ce ions. The 1000ppm sample has the most luminescence intensity and scintillates at wavelength larger than 300nm. An additional canon La(3+) having a closed outer electron shell weakly affects the core-valence trannsetion (CVT), but considerably reduces the intensity of the slow (exciton) component of the luminescence. The fast/slow ratio of the BaF2:1wt%La sample is larger than that of the pure sample. Lanthanum dopant suppresses the slow component and preserves the radiation hardness of undoped BaF2. The emission spectrum excited by X-ray in BaF2:100ppm Eu exhibits two components: a relatively strong slow decay component of the intrinsic luminescence at 300nm, as well as two characteristic weak emission bands of Eu(2+) ions at 430 and 590nm, but shows esaentially no fast component due to their strong self-absorption.