Optical spectroscopy and scintillation mechanisms of Ce[sub [ital x]]La[sub 1[minus][ital x]]F[sub 3]

Journal Article · Wed Jun 01 04:00:00 EDT 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.14880· OSTI ID:7207528

Wojtowicz, A J; Balcerzyk, M; Berman, E; Lempicki, A ^[1]

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1. Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States) ALEM Associates, 303A Commonwealth Avenue, Boston, Massachusetts 02115 (United States)

In this paper we present spectroscopic and scintillation studies of mixed cerium lanthanum trifluoride crystals Ce[sub [ital x]]La[sub 1[minus][ital x]]F[sub 3]. A scintillation mechanism is proposed in which the light output of the Ce[sub [ital x]]La[sub 1[minus][ital x]]F[sub 3] scintillator is determined by three processes: a direct excitation of Ce[sup 3+] ions by secondary electrons and x rays, an ionization of Ce[sup 3+] ions followed by the capture of electrons and formation of Ce bound excitons and, eventually, a transfer of the energy from the electronic-lattice excitations to Ce[sup 3+] ions. These three processes occur in various degrees in [ital all] inorganic Ce scintillators, and the mixed (Ce,La) trifluorides provide, therefore, an excellent example of their relative importance. The peculiarity of fluorides is that Ce[sup 3+] ions occur in regular and perturbed'' sites. The lack of a fast energy migration between the Ce ions and, at the same time, an efficient energy transfer to perturbed'' Ce ions lead to nonexponential decays of the Ce emission. Thermal quenching is moderate and radiation trapping can be minimized, and there is no evidence of luminescence concentration quenching. The light output under [gamma] excitation has a maximum value of about 4500 photons per MeV, which is significantly lower than the estimated conversion-limited value of about 25 000 photons per MeV. It is suggested that the stable Ce[sup 2+] provides electron traps, competing for electrons with holes localized on F[sub 2][sup [minus]] and Ce[sup 4+] ions. Therefore, mostly one process, namely the direct excitation of Ce[sup 3+] ions by secondary electrons and photons, contributes to the light output of CeF[sub 3]. The deomonstrated feasibility of reducing perturbed Ce makes it a strong contender in those applications where high speed, not high light output, is of prime concern.

• DOE Contract Number: FG02-90ER61033; FG02-92ER81360
• OSTI ID: 7207528
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 49:21; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
CERIUM COMPOUNDS
CERIUM FLUORIDES
EMISSION
ENERGY TRANSFER
EXCITONS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM FLUORIDES
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
QUASI PARTICLES
RARE EARTH COMPOUNDS
SCINTILLATIONS
SECONDARY EMISSION