It was recalled that the intensity of the optically excited 3.1eV emission from an irradiated feldspar depended upon the polarization of the 1.45eV exciting light, and that the 3.1eV emission was itself polarized. Dipolar transitions were shown to account for the data in both cases. A method was proposed for using the dipole directions deduced from the data to determine the possible lattice sites of the defects in which these optical transitions occurred. The method worked by assuming that the dipole direction would coincide with a symmetry direction of the crystal field around the defect and then checking the crystal structure for sites where this symmetry direction occurred. Two pairs of dipole directions were deduced from the data for both the excitation and the emission, and the directions of one pair aligned close to approximate symmetry axes in the average geometry of the four O anions around the two T1 sites. It was concluded that transitions in defects occupying T1 sites were the most likely explanation for both the excitation and the emission.

Determining the Possible Lattice Sites of Two Unknown Defects in Orthoclase from the Polarization Effects in Their Optical Transitions. M.A.Short: Journal of Physics - Condensed Matter, 2004, 16[41], 7405-17