Luminescence-quenching model for nuclear recoils in rare-gas liquids for direct dark matter searches

The scintillation efficiency of noble gases for slow ions has been investigated in the context of direct dark matter searches. To estimate nuclear quenching, Lindhard theory is employed. The electronic linear energy transfer, defined as the electronic energy deposited per unit length, is assessed and utilized to determine the initial track structure produced by recoil ions in liquid Ar and Xe. A theoretical model incorporating biexcitonic collision kinetics with diffusion is applied to assess electronic (scintillation) quenching in the liquid phase. In general, Birks' law replicates the numerical calculations with a high accuracy, when the initial track radius is assumed to be constant. The scintillation efficiency for 0.5--250 keV Ar ions in liquid Ar is determined, considering no applied electric field. Despite the variability in the experimental results, a satisfactory correlation is achieved using a quarter hard-sphere cross section.