Investigations of the thermal-shifts and electron-photon coupling parameters for the three spectral lines in LiYF4: Pr3+ crystal

摘要

The thermal red-shifts of the three spectral lines Ei(P-3(0) -> F-3(2b)), E-2(P-3(0) -> F-3(3b)) and E-3(P-3(0) -> F-3(4c)) in LiYF4: Pr3+ crystals are studied by the use of a rational expression where besides the dynamic (or vibrational) effect caused by electron-phonon interaction, the static effect owing to lattice thermal expansion is also contained. It is found from the studies that the dynamic effect gives rise to the thermal red-shift, whereas the static effect leads to the thermal blue-shift. The observed thermal red-shift for the three spectral lines (or peaks) are due to the fact that the dynamic effect is greater than the static one. Even so, the static effect cannot be neglected because when the static effect is also considered, the obtained true electron-phonon coupling parameters alpha' for the three spectral lines E-1, E-2 and E-3 are about 2.25, 1.46 and 1.87 times as great as the corresponding apparent electron-phonon coupling parameters alpha evaluated in the previous paper by the expression including only the dynamic effect. So, the reasonable studies of thermal shift and electron-phonon coupling parameter should take both the dynamic and static effects into account.