1H-ENDR OF DI-t-BUTYL NITROXIDE EFFECT OF THE 14N HYPERFINE INTERACTION
ENDOR spectra of di-t-butyl nitroxide have been observed at −90 °C in heptane. Two ENDOR lines near the free proton frequency had different absorption intensities and their line-shape showed a clear dependence on the nitrogen spin quantum number. This indicates an important spin cross relaxation by the nitrogen nucleus in the proton spin system and suggests a negative sign of the proton hyperfine coupling constant.