An electron nuclear double resonance experiment is described which all
ows the detection of zero-field nuclear quadrupole resonance transitio
ns by observing the unpaired electron spins under field cycling condit
ions. The feasibility of this kind of experiment is demonstrated by th
e detection at 2 K of pure deuteron quadrupole transitions in diamagne
tic molecules of perdeuterated malonic acid crystal irradiated by X-ra
ys.