X-irradiation of Ph₃P⁺CH₂SCH₃CL^- single crystals, at 77 K, gives rise to ESR spectra whose angular variations are characteristic of pairwise trapped radicals. The crystal structure of Ph₃P⁺CH₂SCH₃CL^- is determined and shows that, in the crystal lattice, the proximity and the mutual orientation of two phenyl rings are suitable for the formation of a pair made of a cyclohexadienyl and a phenyl σ-radical. The electron-electron dipolar interaction is calculated for this model and is compared with the corresponding Ɗ tensor. The most probable structure for the cyclohexadienyl radical is deduced from this tensor and agrees with the results obtained from the ¹H and ³¹P hyperfine tensors: the cyclohexadienyl exhibits an appreciable out-of-plane deformation and the phosphonium moiety is located in the equatorial position.