Spectroscopic and optically detected magnetic resonance studies of PO2− in potassium chloride. II. Magnetic resonance analysis

Abstract

The optically detected magnetic resonance (ODMR) spectrum of phosphorus activated potassium chloride crystals obtained at 2 K in zero and weak applied external magnetic fields is reported and analyzed. A theoretical fit to the observed field and angular dependence ofthe ODMR spectrum is obtained using a phenomenological spin hamiltonian, assuming the center to be the paramagnetic photoexcited 3B1 state of the C2v ion PO2−. The components of the phosphorus nuclear hyperfine structure tensor are obtained from the theoretical analysis and compared with those of other AB2 ions and radicals. Optical polarization measurements and weak field ODMR spectra are used to determine the orientation of the PO2− chemical impurity center in the cubic KCl lattice and the orientation is compared with those of other isostructural impurities in KCl. The PO2− chemical impurity center exhibits a dramatic photo-orientation effect at 2 K and is shown to be in thermal equilibrium between twelve crystallographically equivalent orientations at temperatures above 45 K.