Co2+in trigonal fields of oxygen based structures: Electronic absorption spectra of buetschliite-type K2Co(SeO3)2, K2Co2(SeO3)3and zemannite-type K2Co2(SeO3)3· 2H2O

✍ Scribed by M. Wildner; K. Langer

• Publisher: Springer-Verlag
• Year: 1994
• Tongue: English
• Weight: 851 KB
• Volume: 20
• Category: Article
• ISSN: 0342-1791
• DOI: 10.1007/bf00203215

✦ Synopsis

Polarized single crystal absorption spectra, in the spectral range 40 000-5 000 cm-1, were obtained on Co 2+ in trigonally distorted octahedral oxygen fields of buetschliite-type K2Co(SeO3) 2 (I), KzCoz(SeO3) a (II) and zemannite-type K2Co2(SeOa)3.2H20 (III). Site symmetries of Co 2+ are 3m (Dad) in I, 3m (Cav) in II, and 3 (Ca) in III. The spectra can be interpreted on the basis of an electric dipole mechanism, wherein transitions of Co 2 + in the centrosymmetric site in I gain intensity from dynamic removal of the inversion centre by vibronic coupling. In accordance with the elongation of the C006 octahedra along the trigonal axis, the split component E(g) of the ground state 4Wig in octahedral fields is the ground state in all three compounds. Trigonal field parameters Dq~tr~), Dz, Do-and the Racah parameters B have been fitted to the energies of spin allowed transitions (293 K) as follows: