Research on the thermal shifts and electron–phonon coupling parameters of Ri lines for Cr3+ ions in LaGaO3 and LaAlO3 crystals

Abstract

The thermal shifts of Ri lines for Cr3+ ions in LaGaO3 and LaAlO3 crystals are investigated by an expression including both the static contribution due to thermal expansion of lattice and the vibrational contribution due to electron–phonon interaction. The results show that the relative importance of static contributions (characterized by the ratio between the static contribution and vibrational one) is larger than 20% for these systems. So the assumption in the previous papers that the static contributions are very small and can be neglected is doubtful. The true electron–phonon coupling coefficients α' obtained through the above expression are increased by about 30% and 40%, respectively, for LaGaO3:Cr3+ and LaAlO3:Cr3+ in comparison with the corresponding parameters α acquired previously by taking account of only the vibrational contribution. So, in the reasonable and precise studies of the thermal shifts and the electron–phonon parameters for a spectral line in crystals, both the static and vibrational contributions should be contained.