Messung der Photoprotonen aus Argon und Sauerstoff

A thin Cs I(Tl) crystal was used to measure the yield of photoprotous for a 34·5 MeV bremsstrahlung spectrum. The following values relative to the yield of the C¹²(γ, n) reaction were obtained: 2·45±0·35 for argon and 2·06±0·28 for oxygen. An upper limit of the integrated cross section for the (γ, n)- and (γ, p)-reaction in oxygen is given.     

Die Energiespektren der Photoprotonen aus C13 und O18

The energy spectra of photoprotons from C¹³ and O¹⁸ were investigated with 31,5 MeV bremsstrahlung from the Heidelberg betatron using a CsI(Tl)-spectrometer. The spectra are compared to those of C¹² and O¹⁶. Yield values and cross sections are given.     

Energieverteilung und Ausbeute der Photo-α-Teilchen aus Al,Ar, Se und Ag

The energy spectra of photoalpha particles from irradiations of natural Al, Ar, Se and Ag with 32.5 MeV bremsstrahlung were measured between 4 and 16 MeV using solid state detectors. Yield values in μb/MeV · ster were found to be 1.3; 3.0; 0.28; and 0.12 for Al, Ar, Se, and Ag, respectively. Simple compound nucleus calculations show qualitative agreement with the measurements.     

Polarisation und differentieller Wirkungsquerschnitt der Neutronen aus der Reaktion9Be(α,n)12C

The differential cross section and the angular distribution of the polarization of neutrons from the reaction⁹Be(α, n) leading to the ground state of¹²C have been determined at 1.75 and 1.96 MeV energy of theα-particles. The polarization was measured by left-right asymmetry induced by elastic scattering from⁴He. From Blatt, Biedenharn and Simon, Welton theory analysis a set of spectroscopic data has been obtained for five states of the compound nucleus¹³C.     

Photoprotonen aus Kohlenstoff,Stickstoff, Sauerstoff und Neon

The energy spectra of photoprotons from carbon, nitrogen, oxygen and neon were investigated with 30·5 MeV bremsstrahlung of the Heidelberg betatron using a CsI(Tl)-spectrometer. The known resonances could be confirmed, new resonances are found in nitrogen. Yields and cross sections relative to those of the reaction C¹²(γ, n)C¹¹ are given.     

Wirkungsquerschnitt und Winkelverteilung der elastischen und unelastischen Elektronenstreuung in Aluminiumschichten

Absolute intensity measurements of the electrons scattered by a polycrystalline Aluminium foil were carried out in the energy range between 25 and 50 keV. The electrons scattered elastically were separated from those scattered inelastically by means of a retarding field. The intensities of the electrons having passed the foil unscattered and of those which were scattered elastically into the Debye-Scherrerrings and into the continuous background can be interpreted by the assumption of reasonable thicknesses of the crystalline Aluminium and the amorphous Aluminium-Oxide. These values agree approximately with the thickness measured by light absorption. Additionally the probability of the inelastic scattering process can be deduced from these measurements. Investigations of the angular distribution were carried out in order to study the influence of the inelastic scattering on the shape of the primary beam, the rings and the continuous background. The results are discussed in detail. Some results are given in particular, concerning the increase of the half width of the rings due to inelastic scattering processes.     

Die Spektren der Photoneutronen aus O18 und N14

Water enriched to 97% in O¹⁸ and liquid nitrogen were irradiated with 30,5 MeV bremsstrahlung. The energy distribution of emitted neutrons between 2,5 MeV and 20 MeV was measured via the recoil protons in a stilbene scintillator. The energy spectrum of photoneutrons from N¹⁴ shows maxima at 3,0, 6,5 and 11 MeV, whereas that of neutrons from O¹⁸ contains only indication of structure. For both nuclei emission of neutrons seems to proceed mainly through transitions into excited levels of the final nuclei.     

Energieverteilung der von 2, 5, 10 und 15 keV He- und Ar-Ionen an Molybdän ausgelösten Elektronen

The energy distribution of electrons ejected from Mo by He und Ar-ions of 2, 5, 10 and 15 keV has been measured by an electrostatic analyzer of the 127° cylindrical condenser type. The relative number of faster electrons grows with increasing primary energy, but the position of the maximum of the distribution curves (1.9 eV for He and 1.7 eV for Ar) is the same for ion energies of 5, 10 and 15 keV. Only for 2 keV the maximum is shifted slightly towards lower energies.     

Winkelverteilung der Polarisation der Neutronen aus der Reaktion14C(d,n 0)15N bei Deuteronenenergien zwischen 1,3 und 1,9 MeV

Polarization distributions of ground state neutrons emitted from the¹⁴C(d,n ₀)¹⁵N reaction were investigated over the angular range from 15 ° (lab) to 150 ° (lab) at bombarding energies of 1.28, 1.55 and 1.88 MeV. Scattering of neutrons from helium served as polarization analyzer. The experimental results show a large variation with energy of the polarization ranging betweenP(Θ_lab=130 °)=?21% andP(Θ_lab=130 °)=+50% at 1.28 and 1.88 MeV respectively.     

Wirkungsquerschnitt der Reaktion O16 (γ,t)

The tritium yield from irradiation of water with bremsstrahlung was determined in the energy range from threshold to 54,5 MeV. The tritium activity was measured using a low-level gas counter. From a smoothed yield curve, the approximate shape of the cross section was inferred.     

Näherungsweise Bestimmung von Phononenfrequenzen und Kraftkonstanten aus der Temperaturabhängigkeit der Spezifischen Wärmekapazität

Zusammenfassung Die vorliegende Arbeit hat gezeigt, daß sich aus Messungen der spezifischen Wärmekapazität eine Reihe gitterdynamischer Daten mit einer Genauigkeit ermitteln lassen, die eine weitergehende festkörperphysikalische Interpretation erlaubt. Mit den beschriebenen Verfahren eröffnet sich daher auch für andere Strukturen die Möglichkeit, brauchbare gitterdynamische Größen für eine große von Materialien zu bestimmen, für die die inelastische Neutronenbeugung bzw. Ramanmessungen wegen zu großen Aufwandes, unzureichender Probenbeschaffenheit oder aus anderen Gründen nicht optimal eingesetzt werden können.

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Estimation of phonon frequencies and force constants by means of the temperature dependence of the specific heat

From specific heat data several lattice dynamical quantities can be estimated as shown for binary and ternary semiconducting compounds with sphalerite and chalcopyrite structure, respectively. Low temperature C_V-measurements yield an approximation of the acoustic phonon dispersion relations. In addition, for ternary compounds the force constants and the zone centered phonon frequencies may be calculated. The reliability of the procedures described, which, on principle, may be extended to other structures too, is shown by comparison with independent lattice dynamical data.

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Die Autoren danken Prof. Dr. J. Monecke und Prof. Dr. H. A. Schneider für wertvolle Anregungen und Diskussionen sowie O. Bílek, Dr. K. Bohmhammel und Dr. W. Cordts für die gemeinsamen Arbeiten, die zu den beschriebenen Ergebnissen führten.     

Theoretische Aspekte der Untersuchung des Stickstoffmetabolismus mit 15N beim Menschen II. Probleme der Auswertung und Interpretation klinischer Untersuchungen

Klinische Untersuchungen zum menschlichen Stickstoffmetabolismus, die unter Verwendung des stabilen Stickstoffisotops ¹⁵N durchgeführt wurden, werden mit Hilfe eines 3-Compartmentmodells ausgewertet und interpretiert. Möglichkeiten zur Erweiterung dieses Modells werden diskutiert, und durch Computerstudien wird die Aussagekraft der aus Modellen gewonnenen Resultate überprüft.     

Winkelverteilung und Wirkungsquerschnitt der Reaktion6Li(p, α)3He im Energiebereich von 50 bis 190 keV

In the angular distribution 1+A ¹ cos ?+A₂cos²? of the³He particles (cm. system)A ₁ decreases from +0.152±0.018 at 188 keV to ?0.017±0.023 at 62 keV. The slope of the A₁-curve is not approaching zero in this energy range, thereby showing the participation of terms of opposite parity even at very low energies. The total reaction cross section deviates from ans-wave Gamow-plot above appr. 130 keV, being 10 mb at 130 keV. The experimental results are discussed in connection with suggested level diagrams of the compound nucleus⁷Be.     

Analytische Fern- und Laborkontrolle bei der Wideraufarbeitung von Brennelementen aus KKW

The activity of Ni–Cr₂O₃ catalyst for the deuterium exchange reactions between hydrogen and ammonia, as well as for hydrogen and water vapor has been measured in dependence on the reaction temperature and on partial pressure of ammonia and water vapor, respectively. In both cases the activity in dependence on the partial pressure shows a maximum; the maximum of activity for H₂–NH₃ exchange is situated between partial pressures of 0.05 and 0.25, and for H₂–H₂O reaction between 0.25 and 0.5. The Ni–Cr₂O₃ catalyst is about 2.4 more active for the exchange reaction H₂–H₂O than for H₂–NH₃. For both reactions, chromia has a strong promoting effect, enhancing the activity per gram of catalyst of about three orders of magnitude in comparison with that of the Nickel black.