The spectra of iron in orthopyroxene revisited: the splitting of the ground state

Don S. Goldman and George R. Rossman
 Division of Geological and Planetary Sciences
California Institute of Technology
Pasadena, CA  91125


The optical absorption spectra of the M(2) site of orthopyroxene have been reanalyzed, in view of the experimental observation of a mid-infrared band at 2350 cm-1 arising from an electronic transition within the split 5T2g ground stateof the low-symmetry site. This analysis uses C2v spectroscopic symmetry and a crystal-field potential which includes fourth-order harmonic terms. The order ofthe energy states is found to depend upon specific bond angles and lengths. The 2350 cm-1 band is assigned as a transition to the 5B2, state, calculated to lie above the 5A2state. This result indicates that the entire splitting of the5T2g ground state is 2350 cm-1.

low energy band
         The gamma spectrum of hypersthene (top) from Sumit Rock, Oregon, and bronzite (bottom) from Bamble, Norway.                 

last updated: 23-Jul-2023