A quantitative analysis is presented for the electron-spin-resonance spectra of five new defects, which are produced in NaCl:PbCl2 samples by an x irradiation at 77 K and eventual thermal anneal to higher temperatures. The symmetry which is near to orthorhombic along, e.g., (,,[11»0]) axes, and the resolved hyperfine structure lead for all these defects to a model consisting essentially of a trapped electron Pb2 3+ lead dimer center. A quantitative analysis is performed on the g components and the hyperfine interaction in terms of the molecular structure. The absence of Pb2 3+ defects in KCl:PbCl2 samples indirectly demonstrates the different aggregation behavior of divalent impurity-cation vacancy dipoles in both hosts. © 1987 The American Physical Society.