ENDOR INVESTIGATION OF S-2(-), SSE- AND SE-2(-) DEFECTS IN NACL

A single-crystal ENDOR study of S-2(-), Se-2(-) and SSe- defects in Na Cl is presented. ENDOR signals corresponding with interactions with th e nearest neighbouring Na+ ions are found. For each interaction, the s uperhyperfine (SHF) and nuclear quadrupole coupling tensors are determ ined. These ENDOR results can be explained only by assuming a monovaca ncy model, i.e, the S-2(-), Se-2(-) or SSe- ion replaces a single Cl- ion on a lattice site. Analysis of the ENDOR data also reveals that th e nearest neighbouring Na+ ions are displaced with respect to their la ttice position. The size of the defect ions suggests that they will be incorporated into the NaCl lattice under great strain.