【摘要】 本文研究了LaOBr:Ce⁺³,Tb³⁺粉末在液氦温度（4.2K）下的电子顺磁共振,并且进行了晶体场理论计算,理论与实验结果符合得较好,这表明Ce,Tb离子取代了基质中La离子形成发光中心。更多还原

【Abstract】 We have investigated the EPR spectra of LaOBr:Ce3+,Tb3+ powder at liquid helium temperature(4.2K).The EPR signals of three samples with differential concentrations of Ce3+and Tb3+have been obtained on the X-band at 4.2K. The measured results are as follows:ion sample1 2 3Ce3+ g =2.440 g = 2.457Tb3+ g = 3.110 g=3.125The EPR spectra of LaOBr:Ce, Tb powder are computed according to crystalline field theory. The crystalline field Hamiltonian of LaOBr:Ce3+ Tb3+ crystal is computed by means of point charge model. Using Stevens’ “Operator Equivalents”method,we have obtained the crystalline field Hamiltonian operator:where Amn=- |e|γnm const are known as the “crystal field parameters”, and γnm are coefficients which are related to the crystal structure. The particular form of for LaOBr:Ce3+ ,Tb3+is: Using the Hamiltonian operator, we have computed the energy level splitting of Ce3+ and Tb3+ ions in LaOBr crystal by perturbation theory at representations |Lz Sz| and |J Jz| respectively. On this basis the values of g-factor of Ce3+ and Tb3+ ions are obtained:g =2.487 for Ce3+ iong = 3 for Tb3+ ionAccording to the theory of Ibers ’et al., through analyzing the line shape of powder EPR spectra. It is verified that the g -factor of crystal is almost equal to the that of LaOBr:Ce3+ ,Tb3+powder.The calculated result agrees very well with the experimental result. It is thus affirmed that the dopant Ce3+ and Tb3+ions substitute La3+ ions in host material and form luminescence centers.更多还原