Primary scintillation yield and α/β ratio in liquid xenon

Scintillation of liquid xenon due to 5.49 MeV α-particles and 59.6 keV γ-rays, both emitted by a ²⁴¹Am source, was observed. By measuring the amplitudes, A_α and A_γ, corresponding to the peaks due to α-particles and γ-rays on the same spectrum, respectively, the specific light yield ratio (A_α/E_α)/(A_γ /E_γ) (in short, α/β ratio) was found to be α/β=1.01±0.05 at zero electric field. In order to compare with experimental values and theoretical calculations from other authors, usually obtained for 1 MeV electrons, the specific light yield measured for 59.6 keV γ-rays was corrected taking into account its dependence on the γ-ray energy known from the literature. This results in α/β=1.33±0.08 for fast electrons. From our measurements, we estimated the mean energy expended per scintillation photon, i.e., W_s, in liquid xenon as W_s=16.4±1.6 eV for α-particles and 59.6 keV γ-rays and W_s=21.7±2.2 eV for 1 MeV electrons. Our results are compared with those existing in the literature and an analysis of the better precision that can be expected for measurements of the absolute value of the light yield is done