Microscopic Theoretical Calculations of R—Line Thermal Shifts and Broadenings of MgO：Cr^3＋

By taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of basic wavefunctions within d^3 electronic configuration,the values of all the parameters in the expressions of thermal shift (TS) and thermal broadening (TB) due to EPI for the ground level,R level and R line of MgO:Cr^3 have microscopically been evaluated;and then,TS and TB of R line and various contributions to them have uniformly been calculated.The results are in very good agreement with the experimental data.It is found that all the three terms of TS due to EPI are red shifts;the Raman term is the largest one,and the optical-branch term and neighbor-level term are important for TS;the contribution to TS from thermal expansion is blue shift,which is also important.The R-line TS of MgO:Cr^3 comes from the first-order term of EPI.The elastic Raman scattering of acoustic phonons plays a dominant role in R-line TB of MgO:Cr^3 .For both TS and TB,it is very important to take into account all the admixtures of basic wavefunctions within d^3 electronic configuration.

Microscopic Theoretical Calculations ofR-Line Thermal Shifts and Broadenings of MgO:Cr3+

By taking into account all the irreducible representations and their components in t he electron-phononinteraction (EPI) as well as all the levels and the admixtures of basic wavefunctions within d3 elect ronic configuration,the values of all the parameters in the expressions of thermal shift (TS) and thermal broadening (TB) due to EPI forthe ground level, R level and R line of MgO:Cr3+ have microscopically been evaluated; and then, TS and TB of R lineand various contributions to them have uniformly been calculated. The results arc in very good agreement with theexperimental data. It is found that all the three terms of TS due to EPI are red shifts; the Raman term is the largestone, and the optical-branch term and neighbor-level term are important for TS; the contribution to TS from thermalexpansion is bluc shift, which is also important. The R-line TS of MgO:Cr3+ comes from the first-order term of EPI. Theelastic Raman scattering of acoustic phonons plays a dominant role in R-line TB of MgO:Cr3+. For both TS and TB,it is very important to take into account all the admixtures of basic wavefunctions within d3 electronic configuration.