BaF_2中V_k心的ESR谱分析

ESR Spectrum of V_k Centers in Barium Fluoride Crystallites

电子自旋共振(ESR)实验间接表明,γ射线辐照能在室温下在BaF2微晶中产生Frenkel激子这样的元激发,此元激发受热在150℃以下消失。γ射线辐照使BaF2微晶中F-离子上的2P电子跃迁到外层轨道,并与2P轨道的空穴形成紧束缚的电子-空穴对——Frenkel激子。激子中的电子受热脱离F原子,这种晶格上的F0是ESR可探测的顺磁色心点缺陷——Vk心。受γ射线辐照的BaF2微晶中含有Frenkel激子,受热时Frenkel激子湮灭。Vk心增多的现象。

Electron spin resonance(ESR) experiments suggest,Frenkel exciton,an elementary type of excitation,can be induced in BaF 2 crystallites at room temperature by γ ray irradiation.The elementary excitons vanish when the crystallites are heated to less than 150℃.Upon γ ray irradiation,a 2 p electron of the fluoride ion in BaF 2 can be excited to an outer shell orbit,and becomes a tightly bound electron hole pair by coupling with the 2 p orbit hole.The electron acquires more energy upon heating,and leaves the F 0 atom.The F 0 atom thus formed in the lattice becomes a paramagnetic point defect termed as V k center,which can be detected by ESR.The abnormal enhancement of V k signal accompanying the temperature increase indicates,that annihilation of Frenkel excitons brings about the formation of V k centers.