Paramagnetic-Resonance Study of Hyperfine Interactions in Single Crystals Containing α,α-Diphenyl-β-Picrylhydrazyl

Abstract

α,α‐Diphenyl‐β‐picrylhydrazyl, with and without N¹⁵, contained in single crystals of the corresponding hydrazine has been studied by the paramagnetic‐resonance method. All resolved hyperfine effects arise from the two hydrazyl nitrogen atoms. The tensors describing the hyperfine interaction for each nitrogen and the principal‐axes directions have been deduced. The tensors have been interpreted on the basis of an s‐p model with the following electron densities: for the α nitrogen a_s²=0.011 and a_p²=0.263 with the two parts having the same sign of spin density; for the β nitrogen a_s²=0.024 and a_p²=0.396 or a_s²=0.010 and a_p²=0.605. The two choices for the β nitrogen arise from an ambiguity in interpreting the hyperfine tensor, but with either choice the two parts have the same sign of spin density.