Pseudo-Jahn-Teller effect in tetragonal local centers

Abstract

The shape of the light absorption band by a local tetragonal center at the transition Γ₁ → Γ₅(x, y) is investigated in a semiclassical approximation. In addition to interaction with fully-symmetric (Γ₁), Jahn-Teller (Γ₃, Γ₄) vibrations, inter-action is also taken into account with vibrations Γ₅, which “admix” an electron level Γ₄(z) to the electronic state Γ₅, which is separated from Γ₅ by the energetic gap Δ. An analytic computation of the band shape is performed in the first order of the expansion of the form function in Δ⁻¹. An asymmetric two-hump band is obtained, where the long-wave maximum always has higher intensity than the shortwave maximum.