Barium iodide

Abstract: Gamma irradiation was found to release iodine in small amounts from powdered samples of cesium iodide and barium iodide, but not from zirconium iodides. The amount of iodine released was measured using silver foil detectors in sealed capsules that contained the salt. The amount of release was markedly affected by impurities, especially water, that were difficult to control; therefore, G values calculated were inaccurate but of the order of 10/sup -3/ atoms of iodine released for 100 eV of energy absorbed for CsI and BaI/sub 2/ near room temperature. The G values for the zirconium iodides were much smaller. The phenomenon of release of iodine from the ionic iodides by gamma radiation is discussed on the basis of published theories of the formation of defects in solids.

Abstract: We present new results obtained from single crystals of Ba binary halides of BaCl2, BaBr2 and BaI2 activated with Eu2+. While these compounds were known as scintillator materials, due to improvements in the crystal growth process and availability of higher purity compounds, we obtained crystals with better performances than what have been reported before. The luminosities of BaCl2:5%Eu2+, BaBr2:5%Eu2+ and BaI2:5%Eu2+ are about 90%, 70% and 60%, respectively, of their theoretical limit.

Abstract: A MASS spectrometer (radius, 3 in. 45° sector) was used to examine Knudsen cell effusates1. Cylindrical graphite cells had orifice-to-evaporant surface area ratios of approximately 0.03 and were heated by conduction from a resistance furnace and by radiation from a grid above the furnace. The grid was necessary for maintaining axial temperature uniformity in the absence of radiation shielding2. Temperature was measured with a thermocouple attached to the cell base. A movable defining slit between the grid and water-cooled ion-source base made background correction of the ion signals possible; an electron multiplier followed the collector slit. Ionizing electron energies ranged from 7 to 20 eV. Repellers were kept at block potential and spectra were magnetically scanned. Vapour-pressure data (ion signals) were taken at random with respect to temperature; isotopic corrections of ion signals were made when necessary. Each experiment involved a fresh sample.

Abstract: The nitrogen (d 15 N) and oxygen isotope (d 18 O) analysis of nitrate (NO3 ) from aqueous samples can be used to determine nitrate sources and to study N transformation processes. For these purposes, several methods have been developed; however, none of them allows an accurate, fast and inexpensive analysis. Here, we present a new simple method for the isolation of nitrate, which is based on the different solubilities of inorganic salts in an acetone/hexane/water mixture. In this solvent, all major nitrate salts are soluble, whereas all other oxygen-bearing compounds such as most inorganic carbonates, sulfates, and phosphates are not. Nitrate is first concentrated by freeze-drying, dissolved in the ternary solvent and separated from insoluble compounds by centrifugation. Anhydrous barium nitrate is then precipitated in the supernatant solution by adding barium iodide. For d 18 O analysis, dried Ba(NO3)2 samples are directly reduced in a high-temperature conversion system to CO and measured on-line using isotope ratio mass spectrometry (IRMS). For d 15 N analysis, samples are combusted in an elemental analyzer (EA) coupled to an IRMS system. The method has been tested down to 20 mmol NO3 with a reproducibility (1SD) of 0.1% for nitrogen and 0.2–0.4% for oxygen isotopes. For nitrogen we observed a small consistent 15 N enrichment of +0.2%, probably due to an incomplete precipitation process and, for oxygen, a correction for the incorporation of water in the precipitated Ba(NO3)2 has to be applied. Apart from being robust, this method is highly efficient and low in cost. Copyright © 2011 John Wiley & Sons, Ltd.