Influence of hydrostatic pressure on the Jahn-Teller effect in the T-4(2g)excited state of CrCl63- doped Cs2NaScCl6

The T-4(2g)--> (4)A(2g) luminescence of a 4.1% Cr3+ doped Cs2NaScCl6 crysta l is studied as a function of hydrostatic pressure at room temperature and 15 K. The vibrational fine structure observed in the low-temperature variab le pressure emission spectra is analyzed with a two configurational coordin ate approach, involving the totally symmetric a(1g) and the e(g) Jahn-Telle r 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 expan sion 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) exci ted state than on the (4)A(2g) ground state. The absolute Cr3+-Cl- average distance reduction upon increasing pressure is estimated using a simple poi nt charge model. (C) 2001 American Institute of Physics.