Effects of Temperature and Magnetic Fields on the Luminescence of Single Crystal (NH₄)₂TeCl₆

Abstract

The optical absorption of (NH 4 ) 2 TeCl 6 in acetonitrile at room temperature and the luminescence (spectra, decay curves) of single crystal (NH 4 ) 2 TeCl 6 at 1.9 K ≤ T ≤ 180K and at applied magnetic fields H (0 ≤ H ≤ 6 T) are reported. The temperature dependence of the luminescence indicates the existence of a metastable excited state energetically by ~ 80 cm −1 below a second excited state. With H || <111> the decay curves are monoexponential with magnetic field dependent slopes. H ||<001> yields biexponential decay curves, each composed of a slow component corresponding to the decay at H = 0, and of a field dependent fast component. The experimental results can be explained by effects of a tetragonal Jahn-Teller distortion due to a strong coupling of the excited electronic state 3 T lu of the Te(IV) ions and E g vibration modes.