Influence of hydrostatic pressure on the Jahn–Teller effect in the T2g4 excited state of CrCl63− doped Cs2NaScCl6

The T2g4→4A2g 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 a1g and the eg Jahn–Teller normal coordinate. Increasing hydrostatic pressure is found to reduce the tetragonal distortion of the CrCl63− unit in the electronic T2g4 state resulting from the Jahn–Teller effect. Additionally, pressure impedes expansion along the a1g coordinate of the CrCl63− complex upon T2g4→4T2g photo-excitation, and thus has a greater influence on the T2g4 excited state than on the A2g4 ground state. The absolute Cr3+–Cl− average distance reduction upon increasing pressure is estimated using a simple point charge model.