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The refractive index of sodium iodide, an important scintillator material that is widely used for radiation detection, is based on a single measurement made by Spangenberg at one wavelength using the index-matching liquid immersion method (Z. Kristallogr. 57, 494 (1923)). In the present paper, we present new results for the refractive index of sodium iodide as measured by the minimum deviation technique at six wavelengths between 436 nm (n = 1.839 ± 0.002) and 633 nm (n = 1.786 ± 0.002). These six measurements can be fit to a Sellmeier model, resulting in a χ2 of 1.02, indicating a good fit to the data. In addition, we report on ellipsometry measurements, which suggest that the near-surface region of the air sensitive NaI crystal seriously degrades, even in a moisture-free environment, resulting in a significantly lower value of the refractive index near the surface. First-principles theoretical calculations of the NaI refractive index that agree with the measured values within 0.025-0.045 are also presented and discussed. [ABSTRACT FROM AUTHOR] more...

Recent EPR studies of the 4d1 configuration ion Zr3+ in the tetragonal-symmetry orthophosphate hosts LuPO4, YPO4, and ScPO4, have led to additional investigations of d1 configuration ions associated with unusual valence states of other elements. Single crystals of LuPO4, YPO4, and ScPO4 doped with hafnium were grown and the electron paramagnetic resonance (EPR) spectrum of the 5d1 ion Hf 3+ was observed in all three cases. EPR signals due to trivalent hafnium were only observed, however, when the doped samples were gamma irradiated at 77 K and maintained at 77 K during the EPR observations. Since there are two odd isotopes of hafnium with different nuclear spins and different natural abundances, identification of the spectrum of Hf 3+ was straightforward. Since Hf 3+ represents such an unusual valence for hafnium in the solid state, however, this identification was unequivocally verified by preparing crystals doped with isotopically enriched 179Hf. The spectroscopic splitting factors, g|| and g⊥, and the parallel magnetic hyperfine constants A|| of 177Hf and 179Hf were obtained for Hf 3+ in all three hosts. A determination of the hyperfine parameters with the applied magnetic field oriented in the perpendicular direction was not carried out due to quadrupole effects. As in the case of Zr3+, the observed electronic g values for Hf 3+ could not be accounted for by the standard second-order equations which included the spin-orbit-induced admixture of some other excited orbital levels of the d1 configuration into the ground orbital level. The ratio of the nuclear magnetic moments 177μ/179μ, was determined to be 1.2361(4) and 1.2362(3) for hafnium in ScPO4 and LuPO4, respectively. [ABSTRACT FROM AUTHOR] more...

A new scintillator material for the detection of fast neutrons that consists of a methanol adduct of cerium trichloride with the composition CeCl3(CH3OH)4 has been characterized using 14.1 MeV neutrons from a deuterium-tritium neutron generator and fast neutrons from a bare instrumented 252Cf source. The timing resolution of the scintillator for fast neutrons was found to be ~ 1 ns. Neutron interactions in the CeCl3(CH3OH)4 composition were simulated using the MCNP-PoliMi code. These simulations indicate that proton recoils account for most of the deposited energy in CeCl3(CH3OH)4. The crystalline molecular adduct CeCl3(CH3OH)4 represents a rare-earth metal-organic scintillator that can be applied to both fast neutron and gamma-ray detection. [ABSTRACT FROM AUTHOR] more...

A new scintillator material consisting of a methanol adduct of cerium trichloride with the composition CeCl3(CH3OH)4 has been discovered and crystallized in the form of large single crystals by solution growth in methanol. The peak emission of the x-ray-excited luminescence spectrum occurs at ∼364 nm. A light yield of up to ∼16 600 photons/MeV and an energy resolution of 11.4% were obtained using 662 keV gamma-ray photons. The scintillator decay time for 662 keV gamma-ray excitation was measured using the time-correlated, single-photon-counting method, and a nominal value of 64.4 ns was obtained. The molecular adduct CeCl3(CH3OH)4 represents the first example of a rare-earth, metal-organic scintillator that is applicable to gamma ray, x ray, and neutron detection. [ABSTRACT FROM AUTHOR] more...

A new scintillator material for the detection of fast neutrons that consists of a methanol adduct of cerium trichloride with the composition CeCl3(CH3OH)4 has been characterized using 14.1 MeV neutrons from a deuterium-tritium neutron generator and fast neutrons from a bare instrumented 252Cf source. The timing resolution of the scintillator for fast neutrons was found to be ~ 1 ns. Neutron interactions in the CeCl3(CH3OH)4 composition were simulated using the MCNP-PoliMi code. These simulations indicate that proton recoils account for most of the deposited energy in CeCl3(CH3OH)4. The crystalline molecular adduct CeCl3(CH3OH)4 represents a rare-earth metal-organic scintillator that can be applied to both fast neutron and gamma-ray detection. [ABSTRACT FROM AUTHOR] more...