35 GHz CW 1H ENDOR spectra of I (l(N2H4)) obtained at g = 2.02 for samples prepared in H2O (black) and D2O (red) buffers. The lower spectrum shows pulsed 2H ENDOR detected for D2O sample. Conditions for CW ENDOR: microwave frequency, 35.002 GHz (H2O), 35.096 GHz (D2O); modulation amplitude, 2.5 G; time constant, 64 ms; bandwidth of RF broadened to 100 kHz; RF sweep speed, 1 MHz/s, 80 scans; temperature, 2 K. Conditions for pulsed ENDOR: microwave frequency, 34.886 GHz; Mims sequence, π/2 = 52 ns, τ = 452 ns; RF 73 μs; repetition time 12 ms, 16 shots/point, 32 scans; temperature, 2 K.