70Ge(p,gamma)71As and 76Ge(p,n)76As cross sections for the astrophysical p process: sensitivity of the optical proton potential at low energies

The cross sections of the 70Ge(p,gamma)71As and 76Ge(p,n)76As reactions have been measured with the activation method in the Gamow window for the astrophysical p process. The experiments were carried out at the Van de Graaff and cyclotron accelerators of ATOMKI. The cross sections have been derived by measuring the decay gamma-radiation of the reaction products. The results are compared to the predictions of Hauser-Feshbach statistical model calculations using the code NON-SMOKER. Good agreement between theoretical and experimental S factors is found. Based on the new data, modifications of the optical potential used for low-energy protons are discussed.Comment: Accepted for publication in Phys. Rev.

Investigation of 74As decay branching ratio dependence on the host material

The branching ratio between the beta- and beta+/electron capture decay of 74As has been measured in different host materials such as Ta, Al, Ge and mylar. No significant dependence of the branching ratio on the host material has been observed. The half-life of 74As has also been measured in metallic Ta and in semiconductor Ge, no difference has been found and the results are in agreement with the literature value. The obtained results provide an upper limit for the possible host material dependence of the decay rate in 74As.Comment: Accepted for publication in Europhysics Letter

High precision 89^{89}Y(α\alpha,α\alpha)89^{89}Y scattering at low energies

Elastic scattering cross sections of the $^{89}$Y($\alpha$,$\alpha$)$^{89}$Y reaction have been measured at energies E$_{c.m.}$ = 15.51 and 18.63 MeV. The high precision data for the semi-magic $N = 50$ nucleus $^{89}$Y are used to derive a local potential and to evaluate the predictions of global and regional $\alpha$-nucleus potentials. The variation of the elastic alpha scattering cross sections along the $N = 50$ isotonic chain is investigated by a study of the ratios of angular distributions for $^{89}$Y($\alpha$,$\alpha$)$^{89}$Y and $^{92}$Mo($\alpha$,$\alpha$)$^{92}$Mo at E$_{c.m.} \approx$ 15.51 and 18.63 MeV. This ratio is a very sensitive probe at energies close to the Coulomb barrier, where scattering data alone is usually not enough to characterize the different potentials. Furthermore, $\alpha$-cluster states in $^{93}$Nb = $^{89}$Y $\otimes$ $\alpha$ are investigated

Precise half-life measurement of 110Sn and 109In isotopes

The half-lives of 110Sn and 109In isotopes have been measured with high precision. The results are T1/2 =4.173 +- 0.023 h for 110Sn and T1/2 = 4.167 +-0.018 h for 109In. The precision of the half-lives has been increased by a factor of 5 with respect to the literature values which makes results of the recently measured 106Cd(alpha,gamma)110Sn and 106Cd(alpha,p)109In cross sections more reliable.Comment: 3 pages, 2 figures, accepted for publication in Phys. Rev C as brief repor

Precise half-life measurement of the 10 h isomer in 154Tb

The precise knowledge of the half-life of the reaction product is of crucial importance for a nuclear reaction cross section measurement carried out with the activation technique. The cross section of the 151Eu(alpha,n)154Tb reaction has been measured recently using the activation method, however, the half-life of the 10 h isomer in 154Tb has a relatively high uncertainty and ambiguous values can be found in the literature. Therefore, the precise half-life of the isomeric state has been measured and found to be 9.994 h +- 0.039 h. With careful analysis of the systematic errors, the uncertainty of this half-life value has been significantly reduced.Comment: Accepted for publication in Nuclear Physics

Cd110,116(α,α)Cd110,116 elastic scattering and systematic investigation of elastic α scattering cross sections along the Z=48 isotopic and N=62 isotonic chains

The elastic scattering cross sections for the reactions Cd110,116(α,α)Cd110,116 at energies above and below the Coulomb barrier are presented to provide a sensitive test for the α-nucleus optical potential parameter sets. Additional constraints for the optical potential are taken from the analysis of elastic scattering excitation functions at backward angles which are available in literature. Moreover, the variation of the elastic α scattering cross sections along the Z=48 isotopic and N=62 isotonic chain is investigated by the study of the ratios of the Cd106,110,116(α,α)Cd106,110,116 scattering cross sections at E cm15.6and18.8 MeV and the ratio of the Cd110(α,α)Cd110 and Sn112(α,α)Sn112 reaction cross sections at Ecm18.8 MeV, respectively. These ratios are sensitive probes for the α-nucleus optical potential parametrizations. The potentials under study are a basic prerequisite for the prediction of α-induced reaction cross sections (e.g., for the calculation of stellar reaction rates in the astrophysical p or γ process). © 2011 American Physical Society.This work was supported by the EUROGENESIS research program, by the Hungarian Office of the National Scientific Research Fund (OTKA), Grants No. NN83261 and No. K068801, by the European Research Council, Grant No. 203175, and by the Joint Institute for Nuclear Astrophysics (NSF Grant No. PHY0822648). G.G.K. and D.G. acknowledge the support of the Spanish Interministerial Commission of Science and Technology, under Project No. FPA2005-02379, and the Ministry of Education and Science (MEC) Consolider, Project No. CSD2007-00042. G.G. acknowledges support from the Bolyai grant. D.G. acknowledges support from the Spanish Ministry of Science Juan de la Cierva grant. This work was also supported by the Scientific and Technological Research Council of Turkey (TUBITAK), Grants No. 108T508 (TBAG1001) and No. 109T585 (under the EUROGENESIS research program). Fruitful discussions with M. Avrigeanu are gratefully acknowledged.Peer Reviewe

Alpha-induced reactions for the astrophysical p-process: the case of 151Eu

The cross sections of 151Eu(alpha,gamma)155Tb and 151Eu(alpha,n)154Tb reactions have been measured with the activation method. Some aspects of the measurement are presented here to illustrate the requirements of experimental techniques needed to obtain nuclear data for the astrophysical p-process nucleosynthesis. Preliminary cross section results are also presented and compared with the predictions of statistical model calculations.Comment: Accepted for publication in Journal of Physics Conference Series, proceeding of the Nuclear Physics in Astrophysics IV. conferenc

Alpha-induced cross sections of 106Cd for the astrophysical p-process

The 106Cd(alpha,gamma)110Sn reaction cross section has been measured in the energy range of the Gamow window for the astrophysical p-process scenario. The cross sections for 106Cd(alpha,n)109Sn and for 106Cd(alpha,p)109In below the (alpha,n) threshold have also been determined. The results are compared with predictions of the statistical model code NON-SMOKER using different input parameters. The comparison shows that a discrepancy for 106Cd(alpha,gamma)110Sn when using the standard optical potentials can be removed with a different alpha+106Cd potential. Some astrophysical implications are discussed.Comment: 10 pages, 9 figures, accepted for publication in Phys. Rev