Electric field dependence of luminescence due to alpha-particles in gaseous xenon and the energy expended per photon

The scintillation yield of gaseous xenon is measured as the function of electric field strength under the pressures of 1.0 and 2.0 atm. The scintillation yield rapidly decreases as the electric field increases and reaches a constant yield at higher electric field strength. The constant scintillation yield is suggested to determine the Ws-value defined as an average energy expended per photon. In this study, the Ws-value is obtained to be 59.4 ± 1.5 eV and the ratio of average scintillation yield to average ionization one is calculated to be 0.37 ± 0.01, which agrees well to Platzman´s prediction.