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The γ-decay of the anti-analog of the giant dipole resonance (AGDR) to the isobaric analog state has been measured following the p(124Sn,n) reaction at a beam energy of 600 MeV/nucleon. The energy of the transition was also calculated with state-of-the-art self-consistent relativistic random-phase approximation (RPA) and turned out to be very sensitive to the neutronskin thickness (ΔRpn). By comparing the theoretical results with the measured one, the ΔRpn value for 124Sn was deduced to be 0.21 ± 0.07 fm, which agrees well with the previous results. The present method offers new possibilities for measuring the neutron-skin thicknesses of very exotic isotopes. [ABSTRACT FROM AUTHOR]

Spectra of γ rays following the neutron capture at isolated resonances of stable Gd nuclei weremeasured. The objectives were to get new information on photon strength of 153,155-159Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength ΣB(M1)↑, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum ΣB(M1)↑ increases with A and for 157,159Gd it is significantly higher compared to 156,158Gd. [ABSTRACT FROM AUTHOR]

INTEGRAL and RHESSI spacecrafts recently detected the 1.173 and 1.333 MeV γ-ray lines coming from the 60Fe—60Co—60Ni radioactive decay chain. The long lived isotope 60Fe (T1/2 = 1.5 106y) is believed to be primarily produced in core-collapse supernovae. However the interpretation of the observations is difficult because of the large uncertainties concerning 59Fe(n,γ)60Fe and 60Fe(n,γ)61Fe cross sections, involved in 60Fe nucleosynthesis. The direct component of the 60Fe(n,γ)61Fe reaction was studied indirectly via the d(60Fe,pγ)61Fe transfer reaction. The experiment performed in GANIL in spring 2009 will allow to determine the excitation energies of the populated excited states of 61Fe and for the first time their spectroscopic factors as well as their transfer angular momentum. I will first give an overview of the astrophysical context, then I will describe the experimental setup and finally present some preliminary results of the ongoing analysis. [ABSTRACT FROM AUTHOR]

The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ∼1011 cm-3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi-stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of 62Ni, whereas in this case, the number of 63Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier-Leibnitz-Laboratorium in Garching/Munich. The (n,γ) cross section of 64Ni at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source n_TOF of CERN for the future campaign in 2009. [ABSTRACT FROM AUTHOR]

Observations of metal-poor stars in the last decade have revealed an abundance pattern that have recently been explained as the result of two nucleosynthesis processes, a strong r-process that creates most of the Z>=56 and some 38<=Z<=47 abundances and a light element primary process (LEPP) responsible for creating the remaining 38<=Z<=47 abundances and some small contribution to heavier elements. We review some of the current literature on the LEPP and show a derived abundance pattern as a function of mass number. [ABSTRACT FROM AUTHOR]

Neutron capture nucleosynthesis in massive stars has regained considerable interest for the analysis of abundance patterns in very early, metal-poor halo stars as well as for a quantitative picture of galactic chemical evolution. This so-called weak component, which is responsible for the s abundances between Fe and Y, turned out to be very sensitive to the stellar neutron capture cross sections of the isotopes in this mass region. However, these data are incomplete and exhibit large discrepancies between different experiments. New facilities and experimental techniques have to be invoked to meet these challenges. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The “Karlsruhe Astrophysical Database of Nucleosynthesis in Stars” (KADoNiS) project is an online database for experimental cross sections relevant to the s process and p process. It is available under http://nuclear-astrophysics.fzk.de/kadonis and consists of two parts. Part 1 is an updated sequel to the previous Bao et al. compilations from 1987 and 2000 for (n,γ) cross sections relevant to the big bang and s-process nucleosynthesis. The second part will be an experimental p-process database, which is expected to be launched in winter 2005/06. The KADoNiS project started in April 2005, and a first partial update is online since August 2005. In this paper we present a short overview of the first update of the s-process database, as well as an overview of the status of stellar (n,γ) cross sections of all 32 p isotopes. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Many measurements of the 12C(α, γ)16O cross section have been performed up to now but only a few could measure at energies as low as 1 MeV. All of these measurements at low energy have been carried out using Germanium detectors. The low gamma-ray efficiency of these detectors was compensated by very intense beam currents, which may cause considerable uncertainties due to severe target degradation. A verification of these data with a completely different approach, which could reveal systematic uncertainties, was still missing. The realization of such an independent measurement was performed with the Karlsruhe 4π BaF2 array. Due to its high gamma-ray efficiency the beam current could be substantially reduced thus minimizing the thermal load of the target and avoiding sputtering effects. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Considerable effort in experimental nuclear astrophysics, stellar modeling, and observations led to an improved understanding of various nucleosynthesis scenarios in the last decades. This is particularly true for the main s-process in low-mass AGB stars, which is largely responsible for the production of about half of the elemental abundances in the mass range 90≤A≤209. The weak s-process, which produces elements with A≤90, however, is much less understood. Since this process operates in massive stars it is ultimately linked with the abundance contributions of explosive nucleosynthesis in supernovae (SN II). In this field more accurate neutron capture cross sections in the mass range 56≤A≤90 are indispensable for a meaningful comparison of model predictions with observational data. Also, the abundant light elements with A<56 play an important role, since they act as neutron poisons and affect the stellar neutron balance. In this context, the impact of new results for neutron capture cross sections on light and medium mass nuclei will be discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The spectra of γ-rays following the capture of neutrons in 162Dy at neutron energy region of 90–100 keV, where p-wave neutron resonances dominate, were measured for individual γ multiplicities. These data support independently the main assessment from our previous study of the two-step γ cascades, following the thermal s-wave neutron capture in 162Dy, that the M1 scissors-mode resonances are built on all levels of 163Dy, including the levels in the quasicontinuum. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The stellar (n,γ) cross sections of the Ne isotopes are important for a number of astrophysical quests, i.e., for the interpretation of abundance patterns in presolar material or with respect to the s-process neutron balance in red giant stars. This paper presents resonance studies of experimental data in the keV range, which had not been fully analyzed before. The analyses were carried out with the R-matrix code SAMMY including the consistent treatment of possible interferences in the resonant part. With these results the resonant part of the neon cross sections could be determined. If the component due to direct radiative capture is normalized at thermal neutron energies, one finds that the stellar rates had been grossly overestimated. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The last decades have seen an enormous progress in modeling astrophysical objects, which lead to a significantly improved understanding of various nucleosynthesis scenarios. This applies in particular for asymptotic giant branch (AGB) stars where about half of the heavy elements are synthesised by the main component of the s process. In order to test these models and to compare the model predictions with observational data accurate neutron capture cross sections of isotopes with mass numbers A > 90 are indispensable. This holds especially for nuclei near closed neutron shells and in the vicinity of branch points since the analysis of s-process branchings yields important information on stellar parameters like temperature, neutron density, mass density and even convection time scales during the s process. Within this picture neutron reactions on abundant light elements are also important since these act as neutron poisons, hence affecting the neutron balance in the star. Finally, also the most important neutron sources for the s process, 13C(α,n)16O and 22Ne(α,n)25Mg, will be discussed. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

This work is focused on understanding the behavior of the photon strength function of 198Au using a novel approach based on studying γ cascades following the neutron capture in 197Au. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

© 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Behavior of the photon strength function of 198Au is treated using a novel approach based on studying γ cascades following the thermal and keV neutron capture in 197Au. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]