Influence of hydrostatic pressure on the Jahn-Teller effect in the 4T2g excited state of CrCl63- doped Cs2NaScCl6

The T-4(2g)--> (4)A(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 CrCl63- unit in the electronic T-4(2g) state resulting from the Jahn-Teller effect. Additionally, pressure impedes expansion along the a(1g) coordinate of the CrCl63- complex upon (4)A(2g)--> T-4(2g) photo-excitation, and thus has a greater influence on the T-4(2g) excited state than on the (4)A(2g) ground state. The absolute Cr3+-Cl- average distance reduction upon increasing pressure is estimated using a simple point charge model. (C) 2001 American Institute of Physics.