ENDOR investigation of S2–, SSe– and Se2– defects in NaCl

Abstract

A single-crystal ENDOR study of S₂^–, Se₂^– and SSe^– defects in NaCl is presented. ENDOR signals corresponding with interactions with the nearest neighbouring Na⁺ ions are found. For each interaction, the superhyperfine (SHF) and nuclear quadrupole coupling tensors are determined. These ENDOR results can be explained only by assuming a monovacancy model, i.e. the S₂^–, Se₂^– or SSe^– ion replaces a single Cl^– ion on a lattice site. Analysis of the ENDOR data also reveals that the nearest neighbouring Na⁺ ions are displaced with respect to their lattice position. The size of the defect ions suggests that they will be incorporated into the NaCl lattice under great strain.