Results 1 - 10 of 1549
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[en] In-beam spectroscopy studies of 68Ge were made via the 58Ni(12C,pn) and 63Cu(7Li,2n) reactions with the Oak Ridge National Laboratory Tandem Van de Graaff accelerator to produce the carbon and lithium beams. Gamma-gamma coincidences and γ(theta) measurements were performed with high resolution Ge(Li) detectors. A decay scheme was deduced and many new levels and spins were assigned. Lifetimes were deduced from the Doppler broadened lineshapes by using the DSAM technique. Three positive parity bands wee seen above the 6+ yrast state. These results were considered in a rotational alignment model. They provide the first evidence for rotational aligned bands built on both proton and neutron (g/sub 9/2)2 configurations in the same nucleus. Negative parity bands were also observed with the character expected in the rotational alignment model. A similar study was done for 72Ge via the reaction 66Zn(6Li,2n). The yrast band was extended to (8+) and a possible (10+) level was assigned. The bend in the moment of inertia in the yrast band at (8+) in 72Ge suggested that the (8+) level may be a (g/sub 9/2)2 configuration. For both 68Ge and 72Ge one set of levels that can be interpreted as quasi-gamma type vibrational band was also observed
[en] The cross sections for the reactions 63Cu(γ,n)62Cu, 63Cu(γ,np)61Ni, and 63Cu(γ,p) 62Ni are evaluated using the method of global analysis and results of photonuclear experiments that involve significant systematic errors associated with differences in the effective photon spectra and the absolute normalization and energy calibration in individual experiments. The positions of the components with isospins T<=To=5/2 and T>=To+1=7/2 on the energy scale are determined from a comparative analysis of the energy dependences of the cross sections for the reactions 63Cu(γ,p)62Ni and 63Cu(γ,n)62Cu. The parameters of the isospin splitting are determined by fitting the cross sections of the two reactions with the help of appropriate Gaussians. The isospin splitting amounts to δE=E(T>)-E(T<)=U(To + 1)/To=Uo(To + 1)/A=4.8±0.4MeV. The energy of nuclear symmetry is found to be Uo=86.4±7.2MeV. The intensity ratio for isospin components is estimated at R=(σ>-1)/(σ>-1+σ<-1)=0.37±0.02. 25 refs., 5 figs., 5 tabs
[en] The multidetector AMPHORA was used to investigate the reaction of 35 MeV per nucleon 40Ca ions with a natCu target. For 150 000 events corresponding to peripheral and midperipheral collisions, it was possible to reconstruct the primary projectilelike fragments and to calculate event by event the center of mass and the excitation energy. Comparison with a percolation simulation (charge moments, critical exponent) and a momentum ellipsoid analysis are presented and commented. No evidence for a change in disintegration mechanism with increasing excitation energy is found
[en] We measure the masses of of Λ0 and Λ-bar0 hyperons using a very clean sample of 30844 hyperons produced in 230 GeV/c π- Cu interactions and decaying in a silicon vertex detector. Systematic errors were estimated by using K0S decays registered in the same vertex detector. For the averageΛ0/Λ-bar0 mass we obtain (1115:766 ± 0.006 ± 0.042) MeV/c2. The mass difference MΛ - MΛ-bar = (0.015 ± 0.013) MeV/c2 averaged with the E766 result of (-0.012 ± 0.010) MeV/c2 yields (-0.002 ± 0.008) MeV/c2. This confirms the CPT invariance within the accuracy of 7 x 10-6. (author)
[en] One of the important questions in nuclear astrophysics is how the observed abundances of elements came to be. Nearly all of the elements beyond the iron peak are either formed by the s- or the r-process in almost equal shares. The precise s-process path depends on stellar parameters like temperature and neutron density, and on nuclear parameters like half-lifes and neutron capture cross-sections (NCS). Thus, there is a big need for experimental data on the involved reactions to calculate their stellar rates to understand s-process nucleosynthesis. The NCS of the copper isotopes influences the isotopic ratios of Zn. Former experiments concerning the NCS of 63Cu showed large discrepancies. In order to determine the 63Cu(n,γ) cross-section in the astrophysical energy region, an experiment has been performed using the calorimetric 4π-BaF2 array DANCE at the Los Alamos National Lab (LANL). The results of the experiment will be presented.