Scintillation mechanism in helium mixed with xenon

We have been studying scintillation mechanism in helium mixed with xenon. In this study, the time profiles and the luminescence spectra of scintillation in the mixture were measured using a PMT sensitive to photons with wavelength of 115-300nm. Scintillation and ionization yields in He/Xe were measured simultaneously. The time profiles and luminescence spectra depend on not only the xenon pressure but also the helium pressure. Scintillation yields in He/Xe are large as compared with the estimated yields assuming that the energy transfer from helium to xenon does not exist.