Oliver S. Wenger, Rafael Valiente and Hans U. Güdel
Influence of hydrostatic pressure on the Jahn-Teller effect in the ⁴T_2g excited state of CrCl₆^3- doped Cs₂NaScCl₆
J. Chem. Phys. 115, 3819-3826 (2001)                 

Abstract: The ⁴T_2g ⁴A_2g luminescence of a 4.1% Cr³⁺ doped Cs₂NaScCl₆ crystal is studied as a function of hydrostatic pressure at room temperature and 15 K. The vibrational fine structure observed in the low-temperature variable pressure emission spectra is analyzed with a two configurational coordinate approach, involving the totally symmetric a_1g and the e_g Jahn-Teller normal coordinate. Increasing hydrostatic pressure is found to reduce the tetragonal distortion of the CrCl₆^3- unit in the electronic ⁴T_2g state resulting from the Jahn-Teller effect. Additionally, pressure impedes expansion along the a_1g coordinate of the CrCl₆^3- complex upon ⁴A_2g ⁴T_2g photo-excitation, and thus has a greater influence on the ⁴T_2g excited state than on the ⁴A_2g ground state. The absolute Cr³⁺ - Cl^– average distance reduction upon increasing pressure is estimated using a simple point charge model.