Bronisław Rozenfeld

Positron Annihilation in and Compressibility of Water-Alcohol Mixtures

In our recent paper we found that long lived component of lifetime spectrum τ2, which is connected with pick-off ortho-positronium annihilation and its intensity do not change monotonically with the concentration of organic components in water. The results obtained confirm the thesis of quasi-crystalline, clathrate-like structure of water-tetrahydrofuran and water-cyclohexylamine systems. The attempt of the present work was to study the structure of water-ethanol, water-n-propanol and water-isopropanol mixtures, their clathrate-likeness and stoichiometry, if any. The results of our measurements of positronium lifetime, in particular the component τ2 and the intensity I2 as well as the sound velocity data allow us to suppose that in the systems the liquid clathrate-like hydrates are formed. The stoichiometry of these structures was deduced. The results, although obtained using strongly different experimental methods, i.e., positron annihilation and acoustic measurements, are in very good agreement with the clathrate-like concept of the structure of water-organic mixtures.

The electromigration and diffusion of hydrogen in molybdenum

Abstract The electromigration and diffusion of hydrogen atoms in molybdenum were investigated using the resistance method in the temperature range 293–773 K. The following dependence of the diffusion coefficient D and electrical mobility vE on temperature were obtained: D = (5.3 ± 1.53) × 10 −10 exp {− (0.8 ± 0.01) eV kT } { m 2 s −1 } v E = (1.24 ± 0.19) × 10 −8 exp {− (0.9 ± 0.01) eV kT }{ m 2 ( V s ) −1 } . The hydrogen migrates towards the cathode and the effective valency grows with temperature, fulfilling the relation Z eff = (1.42 ± 0.03) − (5.0 ± 0.2) × 10 −8 (Ω m ) ρ ; where ρ is the specific electric resistance.

Effect of the hydrogen concentration on the migration of tritium in a Hall electric field in Ta-H alloys

Abstract The effect of the hydrogen concentration in the TaH x system (0 ⩽ × ⩽ 0.13) on the kinetics of migration of tritium in a Hall electric field was investigated. It was found that the tritium migrates towards the positive Hall electrode. The effective valency of tritium is of the order of 10 3 and the ratio of the effective valency to the thermodynamic factor decreases with increasing concentration of hydrogen. The transverse electric mobility of tritium changes insignificantly with increasing concentration of hydrogen.

A drift of the momentum distribution of annihilating pairs e+e- in Na, Cu and Zn samples conducting electric current

Abstract In this paper we present evidence of the influence of the current carrier mobility on the angular correlation of the annihilation quanta in polycrystalline samples of Na, Cu and Zn conducting electric current.

Investigation of the electromigration of tritium in tantalum

Abstract The diffusion and electromigration of tritium in TaHT systems in α and ϵ phases has been investigated. The diffusion coefficient and the ratio of the effective valency to the thermodynamic factor ƒ were determined from radioactivity measurements of tritium. It has been found that during the phase transformation α → ge the effective valency changes in sign from positive to negative.

Effect of the temperature on tritium migration in a hall field in the Ta-H and Zr-H systems

Abstract The migration of tritium in a Hall field in TaH 0.015 and ZrH 0.015 systems has been investigated in the temperature range 291–576 K. It was found that the tritium migrates towards the positive Hall electrode. The effective valency migration of tritium in a Hall field is of the order of 10 4 -10 6 . The ratio of the effective valency to the thermodynamic factor decreases with increasing temperature for ZrH 0.015 and increases for TaH 0.015 .

Positron annihilation in the vicinity of the critical solution point of methanol-cyclohexane mixtures

Abstract The positron annihilation method was used to investigate critical phenomena in liquid mixtures of methanol and cyclohexane. Anomalies in the annihilation parameters near the critical solution temperature were found.