材料期刊网

A new theory of spectral thermal shifts (TS) has been developed. For the first time, by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI), all the levels and the admixtures of wavefunctions within d(3) electronic configuration, the microscopic expressions for all the parameters in Raman, neighbor-level and optical-branch terms of TS due to EPI have been derived; their values for the R-1, R-2 and ground levels of ruby have been evaluated; the contributions to TS from thermal expansion have also been calculated; and then, the unified calculation of the TS of R-1 and R-2 lines and zero-field splitting (ZFS) for the ground state and the thermal broadenings of R, R' and B line-groups have successfully been accomplished. It is found that the contributions from the second-order term of EPI Hamiltonian H-(2) are dominant in Raman terms of R-1 and R-2 lines; the optical-branch terms play an important role in TS and increase rapidly with temperature and the ones of R-1 and R-2 lines have opposite signs due to the effects of neighbor levels; the neighbor-level terms are very important and it is the admixtures of wavefunctions caused by Coulomb interaction between d electrons and/or trigonal-field and/or spin-orbit interactions that make them nonzero; the contributions to TS from thermal expansion are also important. (C) 2000 Elsevier Science Ltd. All rights reserved.