Crystal field spectra

Ghose S., Kersten M., Langer K., Rossi G. and Ungaretti L. (1986). Crystal field spectra and Jahn-Teller effect of Mn in clinopyroxene and clinoamphiboles from India. Phys. Chem. Minerals, 13 291-305. 

After this preface about the role and uses of intensity calcination I turn now to give some of the details of my past calculations of the intensities of the crystal-field spectra, but mainly I intend to dwell on the reasons which underlie these calculations. 

Analysis of the Crystal-Field Spectra of the Actinide Tetrafluorides. I. Uranium, Neptunium, and Plutonium Tetrafluorides (UF4, NpF4, and PUF4), W.T. Camall, G.K. Liu, C.W. Williams, andM.F. Reid../. Chem. Phys. 95, 7194-7203 (1991). 

Bums, R. G. (1985) Thermodynamic data from crystal field spectra. In Macroscopic to Microscopic. Atomic Environments to Mineral Thermodynamics. (S. W. Kieffer A. Navrotsky, eds Mineral. Soc. Amer. Publ.), Rev. Mineral., 14, 277-316. 

Energy level diagrams and crystal field spectra of transition metal ions... 

Table 3.1. Wavelength and energy units used in crystal field spectra...

Cations with 3d5 configurations have distinctive energy level diagrams and crystal field spectra which are worthy of special attention. The electronic con-... 

Several factors affect intensities of crystal field spectra. In addition to enhancement by increased temperature and pressure discussed in chapter 9 ( 9.4), intensities of absorption bands depend on first, the spin-state or number of unpaired electrons possessed by a transition metal ion second, whether or not the cation is located at the centre of symmetry of a coordination site and third, interactions with next-nearest-neighbour cations. 

Spin-forbidden transitions are possible in other cations with two or more 3d electrons (except Cu2+, 3d9). Thus, in oxygen ligand environments containing Fe2+ ions in octahedral coordination, spin-forbidden transitions also occur in the crystal field spectra, often appearing as weak, sharp peaks in the visible region, in addition to the broad spin-allowed bands located in the near-infrared... 

Taking into account all of the factors influencing intensities of crystal field spectra discussed so far, the following generalizations may be made. Transitions of 3d electrons within cations in octahedral coordination are expected to result in relatively weak absorption bands. Intensification occurs if the cation is not centrally located in its coordination site. In tetrahedral coordination, the intensities of crystal field transitions should be at least one-hundred times larger than those in octahedrally coordinated cations. Spin-forbidden transitions are usually about one-hundred times weaker than spin-allowed transitions in centrosymmetric, octahedrally coordinated cations, but become... 

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