Absorption spectra of Cu 2+ in shattuckite and plancheite

Abstract

Optical and EPR measurements are carried out on shattuckite, a copper bearing silicate. The EPR spectrum observed at 120 K reveales hyperfine structure for parallel and perpendicular components. The measured values are g‖ = 2.402, g⊥ = 2.038, A‖ = 112 × 10 -4 cm -1 and A⊥ = 49.5 × 10 -4 cm -1 and they indicate a tetragonal distortion for the Cu 2+ ion. Further, the constants P and K are evaluated and found to be 0.014 cm -1 and 0.0112 respectively. The bands observed at 8160, 13330 and 16125 cm -1 are assigned to the electronic states of Cu 2+, in a crystal field subjected to tetragonal (C 4V) distortion. The crystal field parameters evaluated are Dq = -1333, Ds = -1565 and Dt = -380 cm -1. Correlating the EPR and optical data, the orbital reduction factors are calculated as k‖ = 0.89 and k⊥ = 0.59. It is confirmed from EPR and optical studies that the Cu 2+ ion in shattuckite is sited in an elongated octahedron. Similar studies are carried out for plancheite. The observed optical absorption spectrum of plancheite is attributed to Cu 2+ sited in an elongated octahedron and tetragonal field parameters are evaluated.