Scintillation efficiency of liquid xenon for nuclear recoils with the   energy down to 5 keV
  The scintillation efficiency of liquid xenon for nuclear recoils has been measured to be nearly constant in the recoil energy range from 140 keV down to 5 keV. The average ratio of the efficiency for recoils to that for gamma-rays is found to be 0.19+-0.02. 
V. Chepel, V. Solovov, F. Neves, A. Pereira, P.J. Mendes, C.P. Silva,   A. Lindote, J. Pinto da Cunha, M.I. Lopes, S. Kossio...