Electron nuclear double resonance at 35000 Mc/s

An ENDOR spectrometer operating at 35000 Mc/s with an ENDOR frequency transition range of 1-500 Mc/s is described. ENDOR transitions have been observed at 300, 77 and 4.2°K. Several systems have been studied at 77°K and the type of information that can be obtained from single crystals, which is obscured in the electron spin resonance, is illustrated. Irradiated succinic acid, sodium formate, glycine, and also unirradiated natural type 1b diamond have been studied. From these measurements one can obtain hyperfine, relative sign, and quadrupole information.