Die potentielle Energie der Wechselwirkung von Elektron und Loch im Ionenkristall

Zusammenfassung In der vorliegenden Arbeit wird die Formel für die potentielle Energie der Wechselwirkung von Elektron und Loch im Ionenkristall abgeleitet und diskutiert, sofern deren Interaktion mit den optischen Gitterschwingungen in Betracht gezogen wird.

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Eine Untersuchung der Elektronenkomponente von Elektronenlawinen im homogenen Feld II

Electron avalanches in uniform fields are studied by means of a short duration spark light source. Electron drift velocities ν_? are measured in hydrogen, nitrogen, oxygen, and some vapours. It is shown, that in hydrogen and nitrogen the number of electrons increases exponentially by gas amplification with a time constant 1/αν_?, in accordance with a conventional assumption and with previous measurements in methane, α is the first Townsend coefficient. In oxygen and air it is, however, demonstrated that the number of electrons increases considerably less than exp (αυ_?·t), and the multiplication process takes longer time. This is evidently due to time losses of the electrons on their paths across the gap. Thus the mean time interval for successors, started by photons at the cathode, is increased. — In addition, this paper gives details of some measurements of the first Townsend coefficient α, the electron diffusion coefficient, and ionic drift velocities for certain gases.     

Eine quantitative Deutung der Elektronengruppen im elektronenstrahlerzeugten He-Niederdruckplasma mit Hilfe der Boltzmannschen Stoßgleichung

Neglecting electron-electron collisions the velocity distribution of plasma electrons in a beam generated He-low pressure plasma is evaluated with help of Boltzmann equation. The energy distribution of secondary electrons generated by the electron beam is considered applying the atom collision theory ofGryzinski. The resulting velocity distribution of plasma electrons shows group character. The “temperatures” of the ultimate and secondary electrons and their density ratio are in satisfying agreement with experiment.     

Zur anschaulichen Diskussion der qualitativen Eigenschaften der galvanomagnetischen Koeffizienten

The dependence of the different components of the conductivity resp. the resistivity tensor upon the strength and direction of an external magnetic field is discussed qualitatively. — In metals, in which the Fermi surface is simply closed, the changes in longitudinal and transversal resistance and the Hall coefficients are large if the anisotropies of the Fermi surface resp. of the scattering mechanism in the planes perpendicular to magnetic field direction are large, and vice versa. In fields, in which this effect already clearly is marked, the changes in transversal resistance in addition increase with increasing anisotropies ink-space perpendicular to Hall field direction, whereas by equal set in of current and Hall field direction the Hall coefficients now show a tendency to decrease with increasing anisotropies perpendicular to magnetic field direction. The order of Hall coefficients may change in high magnetic fields. In contrast to the changes in resistance the Hall coefficients decrease with increasing strength of magnetic field. — In the presence of open Fermi surfaces the transversal resistance doesn't saturate in the direction of the open orbits. If open orbits exist in more than one direction, saturation returns and the Hall coefficients now vanish proportional to 1/B ². In considering open Fermi surfaces it is not allowed to neglect scattering in strong magnetic fields.     

Kernphotoprozesse im Sauerstoff und ihre Bedeutung für die Kontrolle der Energie und des Photonenspektrums an Elektronenbeschleunigern

The yields of the photonuclear reactions¹⁶O(γ,n) and¹⁶O(γ, 2n) are measured with a newly constructed device for fluid samples. The well known structures of the (γ,n) cross section are used for the energy calibration of our accelerator. Though the yield should be strongly dependent on small changes of the bremsspectrum no difference was found, using a thin or a thick target. The conclusion is, that also the thick target is in its effect a thin target under the accelerator conditions. The (γ, 2n) cross section is measured for the first time between threshold and 120 MeV. It is unusually small compared to the (γ,n) cross section.     

Berechnung der Energie und Parameter eines Ionengitters vom Korundtyp

Zeitschrift für Physik A Hadrons and nuclei - Das Korundgitter wird kurz beschrieben. Unter der Voraussetzung eines Koordinationsionengitters und unter Annahme starrer kugelförmiger Ionen...