Luminescence Response and Quenching Models for Heavy Ions of 0.5 keV to 1 GeV/n in Liquid Argon and Xenon

Biexcitonic collision kinetics with prescribed diffusion in the ion track core have been applied for scintillation response due to heavy ions in liquid argon. The quenching factors q = EL/E, where E is the ion energy and EL is the energy expended for luminescence, for 33.5 MeV/n 18O and 31.9 MeV/n 36Ar ions in liquid Ar at zero field are found to be 0.73 and 0.46, compared with measured values of 0.59 and 0.46, respectively. The quenching model is also applied for 80–200 keV Pb recoils in α-decay, background candidates in direct dark matter searches, in liquid argon. Values obtained are ~0.09. A particular feature of Birks’ law has been found and exploited in evaluating the electronic quenching factor qel in liquid Xe. The total quenching factors qT for 0.5–20 keV Xe recoils needed for weakly interacting massive particle (WIMP) searches are estimated to be ~0.12–0.14, and those for Pb recoils of 103 and 169 keV are 0.08 and 0.09, respectively. In the calculation, the nuclear quenching factor qnc = Eη/E, where Eη is the energy available for the electronic excitation, is obtained by Lindhard theory and a semi-empirical theory by Ling and Knipp. The electronic linear energy transfer plays a key role.