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A research program has been started to study experimentally the near-threshold photodissociation of nuclides in the chain of cosmic heavy-element production with bremsstrahlung from the ELBE accelerator. An important prerequisite for such studies is the good knowledge of the bremsstrahlung distribution which was determined by measuring the photodissociation of the deuteron and by comparison with model calculations. First data were obtained for the astrophysically important target nucleus 92Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end-point energies between 11.8MeV and 14.0MeV. The results are compared to recent statistical model calculations. [ABSTRACT FROM AUTHOR]

The distribution of electromagnetic dipole strength in 92, 98, 100Mo has been investigated by photon scattering using bremsstrahlung from the new ELBE facility. The experimental data for well-separated nuclear resonances indicate a transition from a regular to a chaotic behaviour above 4MeV of excitation energy. As the strength distributions follow a Porter-Thomas distribution much of the dipole strength is found in weak and in unresolved resonances appearing as fluctuating cross section. An analysis of this quasi-continuum --here applied to nuclear resonance fluorescence in a novel way-- delivers dipole strength functions, which are combining smoothly to those obtained from (γ, n) data. Enhancements at 6.5MeV and at ∼ 9MeV are linked to the pygmy dipole resonances postulated to occur in heavy nuclei. [ABSTRACT FROM AUTHOR]

The neutron-deficient nucleus68As was populated at high spin in two experiments using the reaction40Ca(32S, 3pn) at beam energies of 105 and 95 MeV. A self-supporting and a gold-backed, highly enriched40Ca target were used. Gamma rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The68As level scheme was considerably extended, especially at negative parity and many previous spin-parity assignments were confirmed or rejected. The total-Routhian-surface (TRS) calculations find shape coexistence and ? softness for the negative- and positive-parity states, respectively. [ABSTRACT FROM AUTHOR]

High-spin states of the neutron-rich vibrational nucleus 114Cd have been studied using the incomplete fusion reaction 110Pd(7Li, p2n) and the GASP spectrometer in conjunction with the ISIS Si ball. About 50 new states with excitation energies up to 7 MeV and angular momentum I < (18+) were observed and for many of them, spin and parity could be firmly assigned. The band-like stuctures in 114Cd are compared to the corresponding ones in the even-even neighbour 112Cd. [ABSTRACT FROM AUTHOR]

The photoabsorption cross section of 181Ta up to the neutron-separation energy is deduced using bremsstrahlung produced with an electron beam of 9.6 MeV energy. The analysis of the measured γ-ray spectra includes the quasicontinuum of levels at high energy. Simulations of γ-ray cascades are performed to estimate intensities of inelastic transitions and branching ratios of the ground-state transitions. The resulting photoabsorption cross section shows enhanced dipole strength in the energy range from 5 to 8 MeV, which may be related to a pygmy dipole resonance. The results of the present experiment are compared with predictions of a quasiparticle-random-phase approximation in a deformed basis. A combination of the present experimental data and (γ,n) data is used as an input to the statistical code talys applied to calculate cross sections and reaction rates of photonuclear reactions that are important for the nucleosynthesis of 180Ta. [ABSTRACT FROM AUTHOR]

One of the greatest questions for modern physics to address is how elements heavier than iron are created in extreme astrophysical environments. A particularly challenging part of that question is the creation of the so-called p-nuclei, which are believed to be mainly produced in some types of supernovae. The lack of needed nuclear data presents an obstacle in nailing down the precise site and astrophysical conditions. In this work, we present for the first time measurements on the nuclear level density and average γ strength function of 92Mo. State-of-the-art p-process calculations systematically underestimate the observed solar abundance of this isotope. Our data provide stringent constraints on the 91Nb(p,γ)92Mo reaction rate, which is the last unmeasured reaction in the nucleosynthesis puzzle of 92Mo. Based on our results, we conclude that the 92Mo abundance anomaly is not due to the nuclear physics input to astrophysical model calculations. [ABSTRACT FROM AUTHOR]

We have carried out photodisintegration cross-section measurements on 861(r using monoenergetic photon beams ranging from the neutron separation energy, Sn = 9.86 MeV, to 13 MeV. We combine our experimental 86Kr(γ, γ')85Kr cross section with results from our recent 86Kr(γ, γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n, γ)86Kr cross section allows us to produce more precise predictions of the 86Kr abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊕, where the 13C neutron source burns convectively rather than radiatively, represent a possible solution for the highest 86Kr:82Kr ratios observed in meteoritic stardust SiC grains. [ABSTRACT FROM AUTHOR]

Abstract: Bremsstrahlung photons produced at the superconducting electron accelerator ELBE of the Forschungszentrum Dresden-Rossendorf will be used for the production of neutron-rich nuclei by photon-induced fission. The properties of such exotic nuclei will be studied by decay spectroscopy. The mass and the charge identification will be based on a new double time-of-flight method for both fission fragments. Currently, an experimental time-of-flight spectrometer consisting of two large-size micro-channel plate detectors with two-dimensional position-sensitive delay-line anodes has achieved a time resolution of 240ps (FWHM) and a position resolution of (FWHM) with a foil thickness of . The spectrometer will also be applied to track beams of exotic nuclei for experiments at the heavy-ion synchrotron (SIS) at GSI, Darmstadt. [Copyright &y& Elsevier]