An EPR–ENDOR study of phosphorus in phenacite

An EPR and ENDOR study on a phosphorus impurity in natural single crystals of phenacite (Be2SiO4) is reported. The EPR studies on this strongly coupled electron–nuclear spin system include the forbidden or ΔMF=0 transitions. The nuclear g factor of the impurity ion which was calculated from an analysis of the forbidden transitions shows the impurity to be 31P. The principal values and directions of the electronic g tensor and the hyperfine coupling tensor were determined through a least-squares fit to the data employing direct diagonalization of the Hamiltonian matrix. ENDOR studies show a superhyperfine (shf) coupling of this center to several near neighbor 9Be nuclei. The shf coupling parameters for three 9Be nuclei were determined and are presented along with a detailed model of the center and a discussion of the crystallographic positions of the Be nuclei. Our analyses indicate a P5+ ion substitutes for a Si ion at a normal site and is converted to P4+ by x rays.