title: Crystal field effect on EPR and optical absorption properties of natural green zoisite.
abstract: In this study the electron paramagnetic resonance (EPR) and optical absorption (OA) of natural crystal of zoisite were investigated after γ ((60)Co) irradiation and high temperature annealing. EPR measurements show that the zoisite from Tefilo Otoni MG Brazil contain Cr(3+), Fe(3+) and Mn(2+) ions and occupy distorted Al(3+) octahedral and tetrahedral sites which are subjected to the action of a strong crystal field in axial direction. Absorption bands which in principle give rise to sets of EPR lines between 500 and 2500 G were found using the deconvolution method. The application of high doses of gamma ray and high temperature annealing has shown no significant effects on EPR and OA spectra. Spin-allowed, spin-forbidden and crystal field parameters were calculated for 3d(3) configuration and interpreted using the spin Hamiltonian formalism containing axial and rhombic terms in low symmetries.
authors.affiliation: Departamento de Física Nuclear, Instituto de Física, Universidade de São Paulo, Rua do Matão, Travessa R, 187, CEP 05508-900, São Paulo, SP, Brazil. henrysjc@gmail.com
authors.forename: Henry
authors.initials: H
authors.lastname: Javier-Ccallata
authors.forename: Shigueo
authors.initials: S
authors.lastname: Watanabe
mesh_terms: D000042:Absorption; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D008872:Microwaves; D008903:Minerals / Q000737:chemistry*; D055620:Optical Phenomena; D011208:Powders; D017640:Silicates / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D008903:Minerals; D011208:Powders; D017640:Silicates