The decay of the new isotope171Re

Irradiating LaF₃-targets with³⁶Ar, the decay of the new isotope¹⁷¹Re was observed for the first time and its half-life determined to be 15.2(4) s. Based on the measuredγ- and X-ray data, a decay scheme could be constructed.     

Double neutron capture in62Ni

The -radiation following single and double neutron capture in isotopically enriched⁶²Ni was studied at the high flux reactor of the Institut Laue-Langevin, using a pair and Compton suppressed germanium detector. Measurements before and after 170 d of breeding were performed. The -ray fluxes through⁶³Ni and⁶⁴Ni are discussed; several new levels and spin-parity assignments were found. On the basis of the known discrete levels and the low-energy neutron resonances, level density parameters were determined within the Constant Temperature Fermi Gas model. The neutron binding energies were measured asB _n (⁶³Ni)=6837.92(18) keV andB _n (⁶⁴Ni)=9657.64(24) keV. The⁶³Ni (n, ) cross section for reactor neutrons was measured to be =20 _–2 ⁺⁵ b.Supported by Deutsches BMFT under contract 06 GÖ 141     

Reaktion von konjugierten doppelbindungsystemen mit dihalogen(diorganylamino)boranen und Na/K-legierung

The reaction of 2,3-dimethylbuta-1,3-diene or 2-methylbuta-1,3-diene with Na/K-alloy and dichloro(diisopropylamino)borane in n-hexane yielded the 1-bora-cyclopent-3-enes, A and II, and 1-bora-cyclonona-1,3-diene, I, respectively. Cycloocta-3,7-diene reacts with dibalogeno(diorganylamino)boranes and Na/K-alloy in n-hexane to yield the 9-bora-bicyclo[4,2,1]non-7-enes III, V, VI and the 1,6-bis(diorganylaminofluoroboryl)-cyclooct-7-enes IV and VH. When 1,2-dimethoxyethane was the solvent, only the dimeric cyclooctene, C, was obtained. The compounds were characterized by elemental analyses and spectroscopy [MS; NMR (¹H, ¹¹B, ¹³C, ¹⁹F)]. An X-ray analysis is presented for I, MNDO-calculations have been carried out for III and III.     

Decay of the new isotope167W

Theα- and β-decay of the new isotope¹⁶⁷W were observed in the reaction of 191 MeV³⁶Ar with¹³⁶Ba using a helium-jet and a fast tape-transport system. The identification is based on coincidences with tantalum X-rays and excitation function measurements. The measured half-life is 19.9(5) s. A decay scheme comprising 12 levels was constructed from γγ-coincidences. The β-decay is discussed within experimental and calculated level systematics. Alpha-rays with energy 4.55(2) MeV were assigned to¹⁶⁷W.     

Critical exponentβ for hyperfine fields in nickel

The magnetic hyperfine fields for⁶³Ni,⁶⁶Cu, and⁶⁷Zn nuclei in nickel metal have been measured by means of perturbed-ray angular distribution techniques at different temperatures up to 1 K below the Curie temperature,T _C . The temperature dependence of the fields can be very well fitted by (1—T/T _C ) with best values=0.322(16) for⁶³NiNi, = 0.427(42) for⁶⁶CuNi, and=0.427(14) for⁶⁷ZnNi respectively. The differences between these exponents indicate that there could be probe atom dependent deviations from proportionality between hyperfine field and bulk magnetization in the critical region.Work performed in partial fulfillment of the requirements for a doctorate in physics at the Freie Universität, Berlin     

Complete spectroscopy of51,52V via the50,51V(n, γ) reactions

The gamma-ray spectra emitted after thermal neutron capture in highly enriched⁵⁰V and^natV targets have been studied using in-pile targets at the ILL high flux reactor and pair and germanium detectors. The neutron binding energies in⁵¹V and⁵²V were determined to beB _n (⁵¹V)=11051.11(17) keV andB _n (⁵²V)=7311.22(26) keV. The thermal neutron capture cross-section in⁵⁰V was measured to be 21 _–2 ⁺⁴ b. From 724 lines attributed to⁵¹V, 330 transitions, comprising 90% of the-ray flux, were placed into the level scheme. Fifty-nine primary dipole transitions from the 11/2⁺ or 13/2⁺ capture states in⁵¹V were established from which the E1 strength distribution was deduced. The energy scaling of these primary transitions was found to follow the E1-giant dipole resonance dominance. Many new levels were established; a number of states proposed in previous (d,p) and (n,) work were confirmed from their primary population and decaying secondary radiations. The density of levels in the high spin (9/2I15/2) region was parametrized with the Fermi gas model. The spin distributions of⁵¹V were analyzed and a spin cut-off parameter =2.8 (3) was deduced. — A nearly complete level scheme of⁵²V up to 3.5 MeV excitation and similar results concerning the level density and the primary -ray spectrum were obtained in the⁵¹V (n, )⁵²V study.Supported by Deutsches BMFT under contract 06GÖ141     

Observation of a new α-ray emitter:168W

Alpha-decay of¹⁶⁸W was identified in¹³⁶Ba(³⁶Ar, 4n) and¹⁴¹Pr(³²S, p4n) reactions. The α-ray energy was measured to be 4399 (12) keV. Using the intensity ratio of the simultaneously detected α-and 178.5 keV γ-rays, I_α/I_γ=4.1(6)·10^?5 the α-branching is discussed.     

The decay of the isotopes176Ir and177Ir

^176,177Ir were produced by irradiation of¹⁴¹Pr with⁴⁰Ar. β-delayed γ-rays of^176,177Ir were observed for the first time. From γγ-coincidence data decay schemes could be constructed. A new half-life of¹⁷⁷Ir was obtained yielding t_1/2=30 (2) s. α-branching ratios of 3.1(6) % for¹⁷⁶Ir and 0.06(1)% for¹⁷⁷Ir were measured.     

Multilayer mirror for x rays below 190 eV

La/B(4)C multilayers have been fabricated by magnetron sputtering for use as x-ray mirrors at energies below 190 eV, particularly for detection of boron K and alpha x rays at 183 eV, their performance has been compared with that of Mo/B(4)C multilayers, which are currently the best-performing multilayers for this energy range. Transmission electron microscopy and synchrotron soft-x-ray reflectometry were used to study the structural quality of the multilayers and their performance as x-ray mirrors. The results show a significant improvement of the peak reflectivity and the spectral purity, indicating that La/B(4)C has a high potential to replace Mo/B(4)C in many x-ray optical applications below 190 eV.