A Study of Cobalt Centers in 3 CdSO<inf>4</inf> · 8 H<inf>2</inf>O Single Crystals

The optical absorption spectra of Co2+ in 3 CdSO4 · 8 H2O single crystals are studied at ambient (300 K) and liquid nitrogen temperatures (80 K). From the nature and position of the observed bands, a successful interpretation could be made assuming octahedral symmetry for the Co2+ ions in the crystals. The splittings observed for the 4T2g(F) band in Co2+ at 80 K is explained as due to the spin—orbit interaction. The band positions are fitted with the four parameters: B = 960 cm−1, C = 3840 cm−1, Dq = 940, and γ = 550 at 300 K and B = 990 cm−1, C = 3960 cm−1, Dq = 940, and γ = 600 at 80 K. The polarized crystal spectra of Co2+ doped 3 CdSO4 · 8 H2O are recorded at 80 K and the three anisotropic bands observed near 8097, 14422, and 18692 cm−1 are presumed to be due to the spin allowed 4T1g(F) → 4T2g(F), 4T1g(F) → 4A2g(F), and 4T1g(F) → 4Tlg(P) transitions of substitutional Co2+ in 3CdSO4 · 8H2O. The observed anisotropy indicates that the 4T2g(F) band is largely magnetic dipole while the other two are electric dipole in nature. Copyright © 1991 WILEY‐VCH Verlag GmbH & Co. KGaA