A study on the thermal red-shift of R1-line for LiAl5O8: Cr3+ crystal from the static and vibrational effects

This paper reports a theoretical study on the thermal red-shift of R1-line (one component of 2E2 → 4A2 transition) for LiAl5O8: Cr3+ crystal by using a full expression including both the static effect derived from the lattice thermal expansion and the vibrational effect coming from the electron-phonon interaction. The results indicate that the vibrational and static effects result in the red-shift and blue-shift of R1-line, respectively, and the static effect in magnitude is about 19% of the vibrational effect. The true electron-phonon coupling parameter is nearly 1.23 times as large as the apparent one which was obtained by considering only the vibrational effect in the previous paper. So for explaining reasonably the thermal-shift of a spectral line in crystals and giving its true electron-phonon coupling parameter, one should take into account both the static and vibrational effects.