The absolute numbers of scintillation photons and electrons produced by 5.49 MeV alpha particles were measured simultaneously in argon, krypton and xenon in the gas pressure range from 1.01 10 5 Pa to 1.01 10 6 Pa. The ratio of the number of excited atoms to the number of electron-ion pairs is an important quantity for understanding the energy pathway of the absorbed radiation energy and was found to be 0.52, 0.55, and 0.60 in argon, krypton and xenon, respectively. The ratios were determined by measuring the number of scintillation photons originating from the excited atoms and the number of electrons. The value of s , which is defined as the average energy to produce one photon, in the case that all of the electron-ion pairs recombine was estimated to be 17.5, 15.4, and 13.0 eV in argon, krypton and xenon, respectively. From the relation between the numbers of electrons escaping from the recombination with ions and the numbers of scintillation photons, it is confirmed experimentally that one scintillation photon is emitted from one recombination process. This means that an excited molecule caused by three-body collisions is not de-excited without emitting a scintillation photon in the vacuum ultraviolet region.
To determine absolute scintillation yields due to alpha particles in high-pressure rare gases, the number of scintillation photons was measured using a vacuum ultraviolet (VUV) sensitive photodiode with spectral quantum efficiency ( ) measured as a function of wavelength . The absolute number of photoelectrons from the photocathode pe was measured using a charge-sensitive preamplifier calibrated with respect to charge number. The collection efficiency for scintillation photons ce at the photocathode was determined from the solid angle subtended by the photocathode at a scintillation point under the condition that there are no photons reflected off the surrounding walls. was determined from = pe ( ce ), where is the average quantum efficiency calculated from ( ) and a relative intensity ( ) of scintillation in rare gases. We measured the luminescence spectra using a VUV monochromator of known efficiency in order to obtain ( ). Measurements were performed in gaseous argon, krypton, and xenon in the pressure range from 1.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.