First measurement of the ionization yield of nuclear recoils in liquid   argon
  This Letter details a measurement of the ionization yield ($Q_y$) of 6.7 keV $^{40}Ar$ atoms stopping in a liquid argon detector. The $Q_y$ of 3.6-6.3 detected $e^{-}/\mbox{keV}$, for applied electric fields in the range 240--2130 V/cm, is encouraging for the use of this detector medium to search for the signals from hypothetical dark matter particle interactions and from coherent elastic neutrino nucleus scattering. A significant dependence of $Q_y$ on the applied electric field is observed and explained in the context of ion recombination. 
T. H. Joshi, S. Sangiorgio, A. Bernstein, M. Foxe, C. Hagmann, I.   Jovanovic, K. Kazkaz, V. Mozin, E. B. Norman, S. V. Pere...
physics.ins-det astro-ph.IM nucl-ex