H.U. Güdel

Scintillation and spectroscopy of the pure and Ce3+-doped elpasolites: Cs2LiYX6 (X = Cl, Br)

The optical and scintillation properties of pure and Ce3+-doped Cs2LiYX6 (X = Cl, Br) are presented. X-ray-excited optical luminescence spectra, optical excitation and emission spectra, time-resolved excitation and emission spectra, scintillation pulse height spectra and scintillation decay time spectra of Ce3+-doped Cs2LiYX6 (X = Cl, Br) crystals measured from 10 to 300 K are presented. Factors influencing the scintillation mechanism and the presence of core?valence luminescence are discussed.

Scintillation properties of RbGd/sub 2/Br/sub 7/:Ce. Advantages and limitations

The scintillation properties of RbGd/sub 2/Br/sub 7/ crystals, doped with Ce/sup 3+/ concentrations of 0.02, 0.11, 0.88, 2.05, 4.1, and 9.8%, are studied under X-ray and /spl gamma/-quanta excitations. For the RbGd/sub 2/Br/sub 7/ sample doped with 9.8% Ce, the authors measured a light yield of 56000/spl plusmn/6000 photons per MeV of absorbed /spl gamma/-ray energy with a main decay time of 43/spl plusmn/1 ns, using a Hamamatsu R1791 photomultiplier (PMT), a /sup 137/Cs radioactive source, and a shaping time of 10 /spl mu/s. A time resolution of 790/spl plusmn/10 ps was measured for the RbGd/sub 2/Br/sub 7/:9.8% Ce compound, using BaF/sub 2/ as second scintillator, two XP2020Q PMTs, a /sup 22/Na source, and an energy threshold set at E/spl ges/511 keV. With the R1791 PMT, an energy resolution of 4.1% (FWHM over peak position) for the 662-keV full absorption peak has been observed for two crystals of 7/spl times/4/spl times/2 mm/sup 3/ and 15/spl times/5/spl times/1 mm/sup 3/ with 4.1 and 9.8% Ce content, respectively. Moreover, the nonproportional responses of three RbGd/sub 2/Br/sub 7/:Ce compounds with different concentrations (0.11, 2.05, and 9.8%) were studied revealing an almost-constant light output response from 17.4 keV to 1 MeV. These properties are compared to three other well-known scintillators: NaI:Tl, CsI:Tl, and Lu/sub 2/SiO/sub 5/:Ce.

Scintillation properties of LuI/sub 3/:Ce/sup 3+/-high light yield scintillators

The scintillation properties of LuI/sub 3/:Ce/sup 3+/(pure, 0.5%, 2%, and 5% Ce/sup 3+/), a new member of the generation of Ce/sup 3+/ doped lanthanide trihalide scintillators, are presented. This material has a calculated density of 5.6 g/cm/sup 3/ and an atomic number Z/sub eff/ of 60.2. Under optical and X-ray excitation, Ce/sup 3+/ emission is observed to peak at 472 and 535 nm. A high light yield of 76 000 photons per MeV (ph/MeV) was measured for LuI/sub 3/:2% Ce/sup 3+/. LuI/sub 3/:Ce/sup 3+/ has a nonexponential decay time. The contribution of short decay components (within 50 ns) to the total light yield is around 50%. An energy resolution (full-width half maximum over peak position) for the 662 keV full energy peak of 4.7/spl plusmn/0.5% was observed for LuI/sub 3/:0.5% Ce/sup 3+/.

Scintillation properties of RbGd2Br7 : Ce3+ crystals; fast, efficient, and high density scintillators☆

Abstract The scintillation properties of RbGd 2 Br 7 crystals ( ϱ ≈ 4.7 g/cm 3 ) doped with Ce 3+ concentrations of 1 and 5 mol% studied under X-ray and γ-quanta excitation are presented and compared with the properties of NaI(Tl) and other scintillators. For a sample doped with 5 mol% Ce, a light yield of about 55 000 photons/MeV with a main decay time of 60 ns was measured. With a photomultiplier tube, an energy resolution of 3.8% (FWHM) for the 662 keV full absorption peak has been observed.

Scintillation properties of some Ce doped chloride elpasolites

Abstract Optical and scintillation properties of Cs2NaLaC6:Ce, Cs2NaCeCl6 and Cs2NaLuCl6:Ce are reported.

Excitation avalanche in Ni2+-doped CsCdCl3

Abstract Nonlinear optical behaviour is observed in CsCdCl 3 :Ni 2+ and compared with a phenomenon reported from lanthanide doped compounds called a “photon avalanche”. Laser power and time dependences are correlated to an appropriate model. An excited-state excitation spectrum is shown.

High-light-output scintillator for photodiode readout: LuI3:Ce3+

In this paper, we investigated the scintillation properties of LuI3:Ce3+. Radioluminescence, light output, energy resolution, and ?-scintillation decay are reported. We find an extremely high light output of 98?000±10?000?photons/MeV. LuI3:Ce3+ also gives a very high electron-hole (e-h) pair response when it is coupled with an avalanche photodiode (APD) (92?000±9000?e?h?pairs?MeV). With an APD, a best energy resolution (full width at half maximum over the peak position) of 3.3%±0.3% for 662?keV ? quanta is observed. A combination of an extremely high light output and a good energy resolution makes LuI3:Ce3+ an ideal scintillator for radiation sensor applications. Some drawbacks due to the hygroscopicity and the difficult growth of LuI3:Ce3+ crystals are also discussed.

Luminescence properties of chromium(V) doped into various host lattices

The luminescence properties of the CrO3−4 ion (3d1) in various host lattices are reported and discussed. The luminescence is due to ligand field transitions and consists of two overlapping emissions due to the doublet splitting of the 2E ground state in lower symmetries than Td. Already at 15 K the luminescence decay times are dominated by fast nonradiative relaxation processes and the luminescence quantum yields at room temperature are 1% or less for all systems. The distortion of the host tetrahedron largely determines the variation of the nonradiative rates for the present materials.

Scintillation properties of K2LaCl5 with Ce doping

Abstract In this work we present the scintillation properties of K 2 LaCl 5 doped with Ce 3+ concentrations of 0, 0.1, 1 and 10%. Under X-ray excitation the crystals show the efficient Ce 3+ (5d–4f) luminescence between 340 and 400 nm. Depending on the Ce concentration, the light yields vary between 24,000 and 50,000 photons/MeV (ph/MeV). Experiments with 662 KeV gamma ray excitation show light yields varying between 13,000 and 30,000 ph/MeV. For Ce luminescence a single exponential decay time of approximately 40 ns is expected. However, for K 2 LaCl 5 :10%Ce, the decay is not single exponential. As a function of the time t , it can be described by a 1/ t 1.63 behaviour for large t . With a crystal of K 2 LaCl 5 :10%Ce we obtained an energy resolution of 5.1% for 662 KeV gamma ray excitation of 137 Cs.

Upconversion excitation of Cr3+ emission in YAlO3 codoped with Cr3+ and Yb3+

We report on upconversion (UC) luminescence in YAl0 3 codoped with 0.3% Cr 3+ and 6% Yb 3+ . At 10 K excitation around 10,400cm -1 leads to red Cr 3 + pair luminescence at 14,000 cm -1 . The UC excitation spectrum of the red Cr 3+ luminescence is very similar to the squared Yb 3 absorption spectrum. This demonstrates that two Yb3 2 F 7/2 2 → 2 F 5/2 excitations are involved in the UC process. From transient measurements, the UC mechanism is found to be dominated by an energy transfer step: Two excited Yb 3+ ions simultaneously transfer their excitation energy to a nearby Cr 3 -pair.