OPTICAL-SPECTRA AND MAGNETIC-FIELD EFFECTS IN CR(III)(L-HISTIDINE)(2)CENTER-DOT(NO3)

We report measurements of the optical absorption and emission spectra in single crystals of Cr(III)(L-histidine)(2).(NO3), with applied magn etic fields up to 5 T, at 1.8 K. The absorption spectrum displays two strong, wide bands due to the electronic transitions (4)A(2) --> T-4(2 ) and (4)A(2) --> T-4(1) Of the Cr3+ ion in a nearly octahedral crysta l field. Besides these bands, we observed weak and narrow absorption p eaks due to the spin-forbidden transitions (4)A(2) --> T-2(1) and (4)A (2) --> E-2 in at least two different crystalline sites, and also the corresponding vibronic lines. The E-2 --> (4)A(2) transition and its v ibronic lines were also observed in the emission spectrum. From these data, we evaluated the Racah and crystal-field parameters of Cr3+ and the g factors of (4)A(2) and E-2. (C) 1998 Elsevier Science Ltd. All r ights reserved.