Field-dependent X-band HYSCORE spectra of 15N PhNadA/8-13C IA (A-D) and corresponding simulations using 13C hyperfine coupling of A(13C) = [1.3, 1.0, 4.0] MHz (E-F, see main text for details). Experimental conditions: temperature, 8 K; MW frequency, 9.4011 GHz; τ, 132 ns; t(π/2), 8 ns; magnetic field, A) 328.4 mT; B) 334.0 mT; C) 345.0 mT; D) 357.0 mT.