[en] We report on the application of ¹⁴N electron nuclear double resonance (ENDOR) at 8.5 T and 239 GHz (λ=1.2 mm) in a γ-irradiated betaine arsenate single crystal. A laser was used as a far-infrared radiation source in a transmission-type electron paramagnetic resonance (EPR) setup without a cavity. The four expected nitrogen ENDOR lines were observed, but due to insufficient saturation of the EPR transitions the signal/noise ratio was not larger than 10 and the signals vanished at temperatures above 20 K. copyright 1995 American Institute of Physics