Durch Zwischengitteratome bedingte Relaxationserscheinungen in kaltverformtem Kupfer

The internal friction of polycrystalline 99,999% purity-copper wires deformed at 23°K to 4% elongation was measured with an inverted torsion pendulum. Besides the wellknown maxima at 50°K (Bordonimaximum) and 165°K a maximum at 250°K was found. From the study of the annealing behaviour and structure of this maximum it is concluded, that the reorientation of dumbbell interstitials in the stress field of the applied force is the process responsible for this internal friction maximum.     

Anregung von Kristallgitterschwingungen durch Elektronenstrahlen

The interaction of electrons with lattice vibrations in thin films of LiF, NaF, MgO, and Al₂O₃ has been studied by means of high resolution electron energy spectroscopy. Just above the excitation energy of the transversal optical modes small bands in the energy loss spectrum are observed. According to the dielectric theory of an unbounded medium only longitudinal optical modes should be excited. The observed energy loss spectrum may be explained by the excitation of surface lattice vibrations. A theoretical energy loss spectrum of LiF has been computed taking into account the surface effects. It is in excellent agreement with the experimental spectrum. Apart from electrons with energy loss also electrons with energy gain were observed. The intensity distribution of the energy gain spectrum is equivalent to the energy loss spectrum. Energy loss and gain spectra of fast electrons by excitation of lattice vibration are corresponding to the Stokes- and Antistokes lines of spectroscopy of light optics.     

Erzeugung polarisierter Elektronenstrahlen durch optisches Pumpen

The valence electrons in sodium vapour were aligned by optical pumping to a polarization between 5% and 15%. An electron beam of 10^?12 A current, 10^?2rad divergency and 1 mm diameter has been obtained by ionisation of the sodium vapour with uv-light. This electron beam was polarized up to 2% as measured by Mott scattering.     

Abnormale Energieunschärfe intensiver Elektronenstrahlen aus Plasmakathoden

Intense electron beams extracted from DUOPLASMATRON-plasma cathodes show a high degree of modulation in intensity and an abnormally large energy spread; these facts cannot be explained simply by the temperature of the plasma electrons and the discharge structure. However, an analysis of the discharge stability behaviour and the interaction of source- and extracted beam-plasma leads to an explanation for the observed effects.

     

Polarisationsmessungen an Elektronenstrahlen nach der Transmission durch magnetisierte Eisenschichten

Magnetized iron foils of a thickness of 500 Å were transmitted by 60 keV electrons. The spin polarization of the electron beam was investigated by Mott scattering after transmission. No polarization effect was found. Since the lowest detectable polarization degree wasP=0·003 the atomic polarization cross section must be assumed to be smaller than 0·8·10^?20cm². This cross section is the sum of the spin exchange cross section and the spin dependent part of the total scattering cross section. If the electron binding energy is neglected, the spin depentend part of the total scattering cross section can be calculated from the theory of Møller scattering. In the case of our conditions-60 keV and an aperture of 10^?3 radian-the calculated cross section is smaller than the experimental upper limit. In further experiments the electron beam was split into the energy spectrum by an electrostatic analyzer placed between the iron foil and the Mott scattering foil. In these measurements only small parts of the energy spectrum were investigated, however, even here no detectable polarization occured.     

Untersuchungen von Relaxationserscheinungen an Quecksilberatomen im metastabilen 63 P 2-Zustand mit einem Impulsverfahren

Zeitschrift für Physik A Hadrons and nuclei - Excitation functions at 90° and 155° to the proton beam have been measured for the reaction41K(p, α)38Ar from 2.1 to 2.5 MeV proton...     

Relaxationserscheinungen im 63 P 2-Zustand des Quecksilber-Isotops199Hg bei Stößen mit Quecksilberatomen im Grundzustand

The decay ofrf resonance signals (Δm _F =± 1, ΔF=0) in the hfs-states (F=3/2, 5/2) of the 6³ P ₂-state of¹⁹⁹Hg has been observed by means of a sampling method. By comparing the relaxation times to those of the even isotopes, the cross section σ₂(F) for the destruction of an alignment in the hfs-states by collisions with ground state Hg-atoms could be measured. The following ratios were obtained: σ₂(F=3/2)/σ₂=1.04±0.06 and σ₂(F=5/2)/σ₂=0.90± 0.03. The cross section σ₂ for the even isotopes was found to be (2.620±0.265) 10^?14cm². Assuming total decoupling of nuclear spinI and electronic angular momentumJ during the collision, the cross sections for the destruction of an orientation (σ₁) and an “octupolarisation” (σ₃) could be calculated. For the even isotopes the following ratios were derived: σ₁/σ₂=0.76 ± 0.07 and σ₃/σ₂=1.08 ± 0.09.     

Radionuclides in deposition in the Ignalina NPP region in 2005

Results of radionuclide activity concentration measurements in deposition and ground-level air conducted at the station of the Institute of Physics situated 3.5 km from the Ignalina Nuclear Power Plant (Ignalina NPP) in 2005 are analyzed. Atmospheric depositional fluxes of ⁷Be, ⁶⁰Co and ¹³⁷Cs are estimated. Radionuclide particle deposition rates are calculated. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model of the global dispersion and deposition is used to explain variations in the ¹³⁷Cs activity concentration in the ground-level air in the Ignalina NPP region in 2005. An increase in the ¹³⁷Cs activity concentration of up to 17.4 μBq m⁻³ on 30 October-5 November is studied. Modelling results show that the Chernobyl NPP Unit 4 Sarcophagus and the radiocaesium resuspension from the Chernobyl NPP accident polluted regions are sources of ¹³⁷Cs to the environment of the Ignalina NPP. Results on solubility in water of aerosols — carriers of ¹³⁷Cs — are discussed.