Detection of 4T1(P) quartet of Co2+ in Zn99.95Co0.05Se monocrystal by optical absorption spectroscopy

Optical absorption spectra of Zn99.95Co0.05Se were recorded at 25 K. The thickness and the concentration of cobalt were Ajusted to obtain sharp d-d* transitions of Co2+ corresponding not only to multiplets of T-4(1) (P) but also to higher excited states. For the first time, a very weak quartet splitting of T-4(1)(P) state was clearly observed and these states were located between 1.464 and 1.517 eV. Higher series of energy states were found to lie in the range 1.98-2.108 eV which are expected on the basis of theoretical calculations but were not detected before and they were tentatively assigned to a lower multiplet of 2G configuration of free ion. The next series of transitions, according to Fazzio et al. is expected to be at 2.5 eV. We did observe a strong absorption band, however, individual transitions were not resolved due to the close separation between them. (C) 2003 Elsevier Ltd. All rights reserved.