t 32g→t 32g transitions of the trans-difluorobis(ethylenediamine)chromium(III) ion. Vibronic analyses and crystal field calculations

Abstract

The 5 K luminescence spectra of trans-[Cr(en)₂F₂]X (X = ClO^–₄, I^–) show extensive vibronic structure which is assigned by comparison with the infra-red and Raman spectra. The emission is from the lower spin-orbit component of the ²E_g(D_4h), ²T_1g(O_h) state to the ground state. Progressions in totally symmetric modes are observed and their intensities are attributed to interaction between the ²E_g components of the ²T_1g(O_h) and ²T_2g(O_h) states. The 5 K absorption spectra can then be assigned and the ²B_1g, ²A_1g, ₂A_2g(D_4h) electronic origins located. The positions of four spinforbidden and four spin-allowed transitions are accurately reproduced by crystal field theory.