  The energy calibration of nuclear recoil detectors is of primary importance
to rare-event experiments such as those of direct dark matter search and
coherent neutrino-nucleus scattering. In particular, such a calibration is
performed by measuring the ionization yield of nuclear recoils in liquid Ar and
Xe detection media, using neutron elastic scattering off nuclei. In the present
work, the ionization yield for nuclear recoils in liquid Ar has for the first
time been measured in the higher energy range, at 80 and 233 keV, using a
two-phase Cryogenic Avalanche Detector (CRAD) and DD neutron generator. The
ionization yield in liquid Ar at an electric field of 2.3 kV/cm amounted to
7.8+/-1.1 and 9.7+/-1.3 e-/keV at 80 and 233 keV respectively. The Jaffe model
for nuclear recoil-induced ionization, in contrast to that Thomas-Imel, can
probably consistently describe the energy dependence of the ionization yield.
