Lineare Polarisation der Bremsstrahlung von 2 MeV-Elektronen

In a preceding work a system of nucleon-antinucleon with the quantum numbers of various existing scalar and pseudoscalar particles was studied with a Bethe Salpeter equation in the ladder approximation. That analysis is now extended to vector particles, that is to bound states with the quantum numbers of theω, ρ, φ. The interaction is produced as in the preceding work byπ mesons, plus a phenomenological vector interaction. The conclusions for scalar and pseudoscalar particles are confirmed also for the vector states: that is to obtain the experimental value for the coupling constant \(g_{N\bar N\pi } \) the used model requires for a cut off values between 1 to 4 nucleonic masses; the effect of the vector interaction is always attractive.     

Beitrag zur Kernspektroskopie an36Cl,90Y und40K durch Messung der Polarisation von γ-Strahlung nach Neutroneneinfang

The circular polarization ofγ-rays following the capture of polarized thermal neutrons in nuclei was measured. The degree of polarization confirmed the spin 2⁺ for the 0.777 MeV level of⁹⁰Y and the spin 0^? or 3^? for the 0.029 MeV level of⁴⁰K. Further theE2/M1 mixing ratio of the 8.58 MeV decay to the ground state of³⁶Cl was measured.     

Messung der Asymmetrie der Bremsstrahlung transversal polarisierter Elektronen

The asymmetry of Bremsstrahlung emitted from transversely polarized electrons is measured for monoenergetic electrons of 300 keV at an emission angleΘ=22±20°. The experiment yields an asymmetryS=?(0.133±0.020)·αZ for a quantum energy of 60 to 240 keV. Exact calculations for the electron-energy used do not exist. The result is not in agreement with calculations in Born approximation. The apparatus is described, the results with all corrections are discussed.     

Messung der zirkularen polarisation von γ-strahlung nach einfang polarisierter thermischer neutronen in kernen

A 70% polarized thermal neutron flux of 6 · 10⁶ s^? was obtained by total reflexion of a 1 m long Co-Fe mirror. Naturel targets of Al, Co, Mo and Sm where exposed to this beam. The measurement of the circular polarization of high energy captureγ-rays yielded some information about nuclear properties: For the transition from the compound state to the ground state in²⁸Al we derived theE2/M1 mixing ratioδ=?2.0 _+1.0 ^?0.5 . In⁹⁶Mo we obtained for the spin of the 2.25 MeV levelJ ^π=2^? or 3^?. If in agreement with theory the spin for this level isJ ^π=3^? the compound state for this decay hasJ ^π=2⁺ for over 50% of the transitions. In accordence with a previous measurement we found for the spins of the doublet in⁶⁰Co at 0.278 and 0.288 MeVJ ^π=3⁺ or 4⁺. For¹⁵⁰Sm we determined the overall circularγ-polarization. The measurement is in agreement with the statistical nuclear model yielding for the compound stateJ ^π=4^?. We confirmed the earlier spin assignementJ ^π=4⁺ for the 0.777 MeV level of¹⁵⁰Sm.     

Messung der Energie- und Winkelabhängigkeit der Asymmetrie der äußeren Bremsstrahlung

In order to obtain an azimuthal dependence of the external bremsstrahlung produced by electrons, the electron beam has to be transversely polarized. In first-order Born approximation the differential cross section does not depend on the azimuthal angle φ¹, but the second-order approximation includes the spin vector of the electrons^2,3 and yields, consequently, a φ-dependence. This paper deals with a measurement of the bremsstrahlung asymmetry as function of the photon energy and the emission angle Θ. The transversely polarized electron beam was produced by momentum deflection of longitudinally polarizedβ-decay electrons emitted from a⁹⁰Sr source. With a kinetic energy of 300±10 keV and a degree of transverse polarization of 74% the electrons hit a Pb target. Because of the high γ-background it was necessary to detect the emitted bremsstrahlung in coincidence with the incident electrons. We found effects of about 3% in contrast to considerably larger values (13%) published in an earlier paper. The asymmetry was numerically calculated according to Johnson and Rozics. Since at an electron energy of 300 keV the Born approximation gives not yet good results, theory and measurement agree only in order of magnitude, particularly at highγ-energies.     

Optische Messung der Hyperfeinstrukturaufspaltungen von CoI-Termen

The spectrum of⁵⁹CoI has been investigated by a direct optical method. The hyperfine-splitting of 61 lines between 3,412 and 6,082 Å has been determined. A special numerical technique has been used to decompose the unresolved profiles. For 36 niveaus theA-factors and from these the magnetic field strength at the nucleus have been obtained and also someB-factors. The accuracy of theA-factors lies between 0.5 and 5 percent.     

Messung der Paarkonversionskoeffizienten von59Co

Internal pair formation propabilities in⁶⁰Ni and⁵⁹Co have been determined by a positron annihilation method. The electrons from the β^?-decay of⁵⁹Fe were measured in triple coincidence with annihilation quanta originating from pairs produced in the deexcitation of the⁵⁹Co nucleus. By this triple coincidence technique it was possible to measure separately the pair formation coefficients Γ for transitions in⁵⁹Co. The observed values Γ_1.29=(3.7±0.4)×10^?5 and Γ_1.10=(0.5±0.1)×10^?5 are in agreement with theoretical calculations forE2-radiation.     

Markierungsprobleme bei der Messung von Verweilzeitspektren in Hochdruckhydrieranlagen

Es wird über Untersuchungen des Verweilzeitverhaltens der flüssigen Phase in einer kleintechnichen Hochdruckhydrieranlage berichtet. Die Messungen wurden mit Hilfe des radioaktiven Nuklids ⁸²Br in Form von Methylenbromid (CH₂Br₂) durchgeführt. Untersucht wurde das Verweilzeitverhalten bei verschiedenen Durchsätzen und unterschiedlichen Betriebsweisen der Anlage, wobei Temperaturen gewählt wurden, bei denen keine Hydrierreaktionen ablaufen.     

Messung der Lebensdauer angeregter Kernniveaus von Gd155

Using two different experimental arrangements, the halflife of the following excited nuclear states in Gd¹⁵⁵ have been measured by the method of delayed coincidences: 60.0 keV-level:T _1/2=(2.4±0.6) · 10^?10 sec, 86.5 keV-level:T _1/2=(6.35±0.09) · 10^?9 sec, 105.3 keV-level:T _1/2=(1.14±0.03) · 10^?9 sec. These results are discussed and compared with the predictions of the collective model.     

Messung der Glorienstreuung des totalen Streuquerschnitts von Na-Hg

The velocity dependence of the total cross section of Na-Hg has been measured in the velocity region from 750 to 2700 m/s. The extremaN=5.0 toN=11.0 are well resolved. The glory extrema indexing was performed by counting the number of measured rainbow extrema in the differential cross section at corresponding velocities. The results from the data evaluation method proposed by Bernstein and O'Brien are compared with the results from an inversion procedure for this system. Significant errors can result from the use of the Bernstein-O'Brien method except in the case of the expressiona ₁?r _m .