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