Scintillation mechanism in stoichiometric cerium compounds
Conference
·
OSTI ID:10162989
- Boston Univ., MA (United States). Dept. of Chemistry
These materials constitute a new class of scintillator media, with high speed and high light output. This is illustrated using CeF{sub 3}, and CeP{sub 5}O{sub l4}. While speed, being limited by a radiative lifetime of an allowed d-f transition on the Ce{sup +3} ion, cannot be improved (without loss of the light output), the light output in both cases falls significantly below the estimated theoretical limit. To explain this we propose a mechanism of scintillation process, in which transfer of excitation energy from the lattice to the d-f electronic structure of Ce{sup +3} ions is absent and the light output of the scintillator is limited to the excitation energy directly intercepted by Ce ions. The efficiency depends, therefore, on the competition for holes between Ce{sup +3} ions and anions, determining the share of the total energy deposited by a high energy particle, which can be transformed into scintillation photons. The mechanism requires that the Ce ion has a stable 4+ charge state. Ionization of Ce{sup +3} is followed by capturing of an electron and creation of the Ce bound exciton. In the next step the energy of the bound exciton is transferred to the d-f structure of the Ce ion and, in the final step, a scintillation photon is emitted. The relatively high light output characteristic of these materials is due to the high concentration of Ce ions. The reasons for the lack of efficient energy transfer from the lattice may reside in large relaxation energies of lattice excitations. We use this model to discuss potential improvements in the light output of CeF{sub 3}.
- Research Organization:
- Boston Univ., MA (United States). Dept. of Chemistry; ALEM Associates, Boston, MA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-90ER61033; FG02-92ER81360
- OSTI ID:
- 10162989
- Report Number(s):
- CONF-9209253--5; ON: DE93015499
- Country of Publication:
- United States
- Language:
- English
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