[en] Temperature cw-EPR and pulsed EPR electron spin echo experiments were performed for a low concentration of Cu²⁺ ions in cubic SrF₂ crystals. The well resolved EPR spectrum at low temperatures (below 30 K) with parameters g_parallel = 2.493, g_{perpendicular} = 2.083, A_parallel = 121, A_{perpendicular} = 8.7, A_parallel (¹⁹F) = 135, A_parallel (¹⁹F) = 33.0 (A-values in 10^-4 cm^-1) is transformed continuously into a single broad line above 225 K on heating, due to the g-factor shift and EPR line broadening. These data along with the angular variation EPR data are described in terms of a pseudo-Jahn-Teller effect of (T_2g+A_2u)x(a_1g+e_g+t_1u) type producing six off-centre positions of the Cu²⁺ ion in the fluorine cube. Above 30 K a two-step averaging g -factor process occurs and is governed by vibronic dynamics between potential wells of the off-centre positions. This dynamics governs the electron spin relaxation in the whole temperature range. The electron spin-lattice relaxation rate 1/T₁ grows rapidly by six orders of magnitude in the temperature range 30-100 K and is determined by the Orbach-type process with excitations to two excited vibronic levels of energy 83 and 174 cm^-1. For higher temperatures the relaxation is dominated by overbarrier jumps leading to the isotropic EPR spectrum above 225 K. The phase memory time T_M has the rigid lattice value 3.5 μs determined by nuclear spectral diffusion and its temperature variation is governed by the vibronic dynamics indicating that the excitations between vibronic levels produce a dephasing of the electron spin precessional motion. (author)

[en] The influence of SrF₂ nanoparticle size on their luminescence and kinetic properties under photo- and X-ray excitation was studied. The self-trapped exciton luminescence intensity was shown to reveal dependence on both the nanoparticle size and the range of excitation energies. The lowest sensitivity to the nanoparticle size is observed in the case of excitation in the region of optical exciton formation. The recombination of electrons with surface defects and non-radiative decay of excitons due to diffusion to the surface is found to be the determining factors of the luminescence quenching in the case of X-ray excitation.

[en] Using the automated spectrometer and special-purpose software, superfine interaction has been studied for the first time and coordinates of ¹⁹Fe nuclides have been defined for four anionic spheres in tetragonal centers CaF₂. The structural data obtained are compared with the results of the theoretical calculations published

[en] Poster presentation

[en] A modest proof-of-principle effort has been conducted to investigate melt casting as a process for compacting SrF₂ to near theoretical density. A nonradioactive SrF₂ mixture, similar in chemical composition and method of prepartion to SrF₂ encapsulated at the Hanford Waste Encapsulation and Storage Facility (WESF) was used for the test evaluations. Hard, dimensionally stable, monolithic ingots that are >98% of theoretical density have been produced. Significant chemical purification from Al, Fe, Cr, Ni, Na and Zr has been demonstrated

No abstract available

No abstract available

[en] A modest proof-of-principle effort has been conducted to investigate melt casting as a process for compacting SrF₂ to near theoretical density. A nonradioactive SrF₂ mixture, similar in chemical composition and method of preparation to SrF₂ encapsulated at the Hanford Waste Encapsulation and Storage Facility (WESF) was used for the test evaluations. Hard, dimensionally stable, monolithic ingots that are >98% of theoretical density have been produced. Significant chemical purification from Al, Fe, Cr, Ni, Na, and Zr has been demonstrated

[en] The influence of Ba, Sr, Ca, Mg cations on transfer numbers of fluorine in glasses of Ba(PO₃)₂ - MeF₂ pseudobinary systems is studied. Transfer numbers are essentially different in one and the same fluorine ion concentration in glasses, containing various alkali-earth cations: increase of the cation field force brings about decrease of the transfer numbers of fluorine, and the glass-formation region in the Ba-Sr-Ca-Mg series rises. The dependence of transfer numbers of fluorine on the fluorine concentration logarithm is presented. It is established, that alkali-earth metals influence the transfer numbers of fluorine on account of selective interaction with the phosphate constituent of glass structure

No abstract available