Stress-induced optical dichroism of V--centers in MgO

The stress-induced optical dichroism and optical spectra of the V--centers in electron irradiated MgO are reported. The dichroism spectrum can be largely attributed to a paraelastic alignment of inherently-dichroic V--centers. A curve-fit analysis of the lower-energy portions of the dichroism and absorption spectra yields the ratio of the transition dipole strengths, D(parallel)/D(perpendicular) = 1.55 +- 0.2, and the energy splitting, E(parallel)/E(perpendicular) = 0.22 +- 0.07 eV, for light polarized parallel and perpendicular to the defect symmetry axis. The spectra also have considerable intensity in their high-energy tails, and it is speculated that a portion of this intensity is due to the V-center. The implications of the results with regard to the electronic structure of the center are discussed. (author)