Thallous Iodide Research Articles

X-ray and UV photoemission studies of the thallous iodide phase transformation

The orthorombic to simple cubic thallous halide phase transformation induced by temperature increase is studied by means of X-ray and UV photoelectron spectroscopy. The structural transformation is well evidenced by an abrupt decrease of the binding energy separation between the iodine and the thallium core levels at the phase transition temperature. Valence band spectra recorded for both crystal forms by using the HeI radiation evidence modification in the band structure.

Magneto-Optical Absorption in Thallous Iodide of CsCl Structure

Magneto-optical absorption due to exciton is investigated for thallous iodide of CsCl structure at low temperatures. By the application of magnetic field appear the absorptions due to 2s and 3s excitons which are not observed in zero magnetic field. One-phonon replicas of zero-phonon excitons are found to grow and exciton polaron pinning effect is observed in high magnetic field. The exciton binding energy is determined as 11±1 meV and its reduced mass as (0.25±0.05) m 0 . The dielectric constant effective to the exciton binding and the longitudinal optical phonon energy are estimated to be 17±2 and 11±2 meV, respectively.

On Photographic Behaviour of Vacuum Deposited Layers of Lead and ThaIIous Iodide

Utilizing the motion of photogenerated holes, a new photographic direct positive system was developed and now its properties, when using lead and thallous iodide, are studied. It is found that best photographic characteristics of the layers are obtained at a thickness 0.3-0.6µ for lead iodide and 0.2-0.4µ for the thallous iodide. A strong dependence of the sensitivity on the type of the fogging metal, both for lead and thallous iodide is observed. The sensitivity decreases considerably when the photosensitive layer is fogged with copper or tin instead of with silver, probably due to the different valency of the metals.

The electrical conductivity and the phase transformation of thallous iodide single crystals

The temperature-dependent specific electrical conductivity of zone-refined TlI single crystals was measured in the temperature range between 400 and 600 °K. Repeated measurements of the same crystal samples resulted in annealing effects in the course of which metallic-grey precipitates were formed. The conductivity in the transformation range can be explained by the formal kinetics of a diffusion-controlled nucleation and growth process. An estimation of the activation energy of the formation of the second-phase nuclei in the parent phase by the evaluation of TTT curves yields energy values of 0.2 to 0.4 eV.

Thallium Nuclear Magnetic Resonance in Thallous Iodide

Wide-line nuclear magnetic resonance techniques have been used to investigate the electron coupled (or indirect) spin exchange interactions and chemical shifts of the two thallium isotopes in thallous iodide. Thallous iodide undergoes a phase transition near 160°C from a layered orthorhombic structure to a cubic (CsCl) structure. An order-of-magnitude decrease in the estimated second moments of both thallium lines was observed in going from the orthorhombic to the cubic structure, and while the two thallium lines were the same width in the orthorhombic phase, the second moment of the 203Tl line was 50% greater than the second moment of the 205Tl line in the cubic phase. These results are interpreted in terms of a decrease in the “covalent character” of the bonding in the solid, with the transition to the cubic structure. This is consistent with the structural changes occurring at the orthorhombic to cubic transition which involve the lengthening of some unusually short thallium–iodine bonds to form a more symmetric solid with a higher density. The thallium chemical shift in the cubic phase was found to be − 15 × 10−4 (relative to a saturated TlF solution). An analysis of the chemical shifts of the broad lines in the orthorhombic phase was not conclusive as the shifts were field dependent.

The Scintillation Mechanism in Thallium Doped Alkali Halides

In the scintillation mechanism for alkali iodides doped with thallous iodide: 1. Most of the luminescence, and possibly all of it, is from recombination and therefore energy transfer is predominantly from charge transport to thallium. 2. There are two modes of recombination at thallium which differ in the sequence of charge trapping at Tl+. The electron may be trapped before a mobile hole recombines with it, or the hole may be trapped before recombination with a free electron. 3. Thermal hole diffusion is an important process at room temperature and determines which mode a recombination event follows. 4. Both modes of recombination are active. 5. There is non-thermal hole trapping which is a significant part of the scintillator mechanism.

The optical absorption of orthorhombic thallous iodide

The optical absorption of strain reduced thallous iodide films has been measured. Strong absorption of the order of 10 5 cm -1 is observed and a number of relatively sharp lines appear. An exciton-longitudinal optical phonon coupled state sideband to the first exciton peak is observed. Die Lichtabsorption in deformationsarmen Thallojodidschichten wurde gemessen. Starke Absorption in der Grossenordnung von 10 5 cm -1 wird beobachtet, cine Reihe von verhaltnismassig ausgepragten Linien kommen zum Vorschein. Eine Nebenbande eines gekoppelten Zustandes aus Excitonen und Langs-Lichtphononen wird and der 1. Excitonenspitze beobachtet.

Organothallium compounds : V. Reactions of bis(pentafluorophenyl)thallium(III) compounds with iodide ions

Bis(pentafluorophenyl)thallium(III) compounds, (C 6F 5) 2TIX (X = Br, Cl, 1 2 SO 4, OAc, etc.), are decomposed by iodide ions in boiling aqueous ethanol, aqueous methanol, or water with the formation of thallous iodide and pentafluorobenzene. Analogous reactions are possible with bromide or cyanide ions. However, reaction with acidified iodide or bromide ions gives the corresponding tetrahalothallate(III) complex. The formation of thallous iodide in reactions without added acid is attributed to intermediate formation of the tetraiodothallate(III) complex and base, which then interact to give thallous iodide. The ready decomposition of MTII 4 (M = Bu 4N or MePh 3As) complexes by base to give thallous iodide has been demonstrated. Under suitable conditions, cleavage of bromobis(pentafluorophenyl)thallium(III) with iodide ions gives the triiodopentafluorophenylthallate(III) complex, which has been isolated as the tetrabutylammonium or the methyltriphenylarsonium salt. The new compounds (C 6F 5) 2 TIX (X = I or CN) have been prepared by metathesis between sulphatodi[bis(pentafluorophenyl)thallium(III) and iodide or cyanide ions in water. They are considered to be dimeric with bridging iodide or cyanide groups.

Polymorphism, compressibility and thermal expansion of thallous iodide

Thallous iodide (TlI) transforms from a layer orthorhombic (Cmcm) structure to a cubic CsCl-type structure with increasing temperature and/or pressure. We have studied the transition as a function of combined hydrostatic pressure and temperature. We also measured the compressibility (at 20°) and thermal expansion (at 1 bar) of both phases, as well as the latent heat of transformation. With increasing temperature at 1 bar, the transition temperature is 169±2°. The average transition temperature of the increasing and decreasing temperature cycles is 156±2°, and it decreases monotonically with increasing pressure with an initial slope of −53±3°/ kbar. At 25°, the transition to the cubic phase occurs at 4.70±0.10 kbar and the reverse transition at 1.15±0.10 kbar. The initial volume compressibility of the orthorhombic phase is (7.55 ± 0.20) × 10 −3 kbar −1, and the compressibility of the cubic phase at 6 kbar is (5.10±0.20) × 10 −3 kbar −1. The volume decreases 3.3 per cent at the transition. The lattice parameters of both phases increase linearly with temperature over the range covered. The mean linear coefficients of thermal expansion for the orthorhombic phase between 23 and 170° in units of 10 −6 oC −1 are: α a = 15-9±0.5, α b , = 48.7±0.3, and α c = 60.4±0.6. That of the cubic phase between 170 and 300° is α a = (51.0±0.3) × 10 −6 o C −1. The measured latent heat is 293±38 cal/ gm mole where 321 cal/gm mole is calculated from the Clapeyron equation. The structural and thermodynamic aspects of the transformation are discussed.

Insulator-to-metal transition at high pressure

One of the most interesting of the physical phenomena of materials investigated under pressure is the transition to the metallic state exhibited by some insulators and semiconductors. Experimental results concerning this transition in a number of substances are reviewed and discussed. The transition to the metallic state under high pressure occurs by one of two mechanisms. In the first, the metallic state is reached as a result of a continuous decrease and eventual disappearance of the energy gap. This case is exemplified by the pressure behavior of thallous iodide and iodine. In the second mechanism, the metallic state appears discontinuously as a result of a first-order phase transformation to a more closely packed lattice. The transitions in silicon, germanium, and some group III-V and II-VI compounds offer good examples of the latter mechanism. Possible geophysical implications of the results are discussed.

Production of Carrier-Free 132Cs and 129Cs

Carrier-free 132Cs and 129Cs were produced by the 129I(α,n)132Cs, 129I(α,4n)129Cs, and 127I(α,2n)129Cs reactions using thallous iodide as a recoverable target. Upper limits for the production yields of these isotopes are 25µC/(µA h) for 132Cs and 2 mC/(µA h) for 129Cs, for 35-MeV alpha particles.

Photometric determination of traces of silver in uranium metal

The sample was dissolved in nitric and sulfuric acids followed by the additions of thallous sulfate and potassium iodide. The silver coprecipitated with thallous iodide was taken up in sulfuric acid and hydrogen peroxide. The solution was evaporated to dryness and the residue was treated with acetic acid (60 vol%) and p-dimethylaminobenzylidenerhodanine (0.0041%). The light absorbency at 580 m mu indicated the amount of silver. 0.4 approximates 4 ppm silver in uranium metal could be estimated, provided 5 g sample was taken and was made up into 5 ml of the colored solution. The coprecipitation rate with thallous iodide was confirmed to be more than 95%, by using Agllom as a tracer. (auth)

陽極溶出電量分析法による金属ウラン中の微量銀の定量

Trace amounts of Ag in metallic U were determined by anodic stripping coulometry. For samples containing less than 0.4 ppm Ag, Ag was separated from U by coprecipitation with thallous iodide; then the precipitate was dissolved with a sulfuric acid-hydrogen peroxide mixture. The solution was evaporated to dryness, and Ag was determined by anodic stripping coulometry. For samples containing more than 0.4 ppm Ag, it could be determined in the presence of the large amount of U without preliminary separation. In the latter case. the effect of U was suppressed by formation of citrate complex. Satisfactory results were obtained by both methods. The effects of volume and pH of the electrolyte solution were also studied. For 10 ml of the electrolyte solution, 80-min electrodeposition was advisable, where 0.1 to 2 g Ag was to be determined. For 20 ml, 3-hr electrodeposition was advisable, where 0.3 to 2 g Ag was to be determined. Variation of pH (3 to 7) of the electrolyte did not influence the dissolution curve area. (H.H.D.)

The Photo–oxidation of a Chlorophyll ‘Preparation

Examination has been made of the photo–oxidation in white light of a chlorophyll preparation on various solids by the direct measurement of oxygen pressure decrease.Rates were very low on glass, zinc oxide, aluminium oxide, thallous phosphate, and ferric phosphate, but were some ten times more rapid on thallous bromide and thallous iodide. No change in rate with thallous bromide preparations was observed in the presence of water vapour and carbon dioxide. The quantum efficiency on glass was of the order of 10˜8 for blue light.The oxygen: chlorophyll and the oxygen: carotene molecular ratios of the final photoproduct were almost exactly unity. The final stable product is regarded as a hydroperoxide: partial reversibility of the oxidation was observed by simple pressure reduction.In general, the course of the oxidation resembles that of some other organic molecule oxidations, being characterised by an induction period, by a constant–rate portion, and by a subsequent rate of oxidation slowly decreasing to zero.

319. Methylation of α-methylglucoside by thallous hydroxide and methyl iodide

319. Methylation of α-methylglucoside by thallous hydroxide and methyl iodide

The solubility product of thallous iodide at 25°

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The Potential of the Thallium Electrode and the Free Energy of Formation of Thallous Iodide

The Potential of the Thallium Electrode and the Free Energy of Formation of Thallous Iodide