0 Ju l 2 01 5 First Measurement of the 96 Ru ( p , γ ) 97 Rh Cross Section for the p-Process with a Storage Ring

Bo Mei, 2 Thomas Aumann, Shawn Bishop, Klaus Blaum, Konstanze Boretzky, Fritz Bosch, Carsten Brandau, Harald Bräuning, Thomas Davinson, Iris Dillmann, Christina Dimopoulou, Olga Ershova, Zsolt Fülöp, Hans Geissel, Jan Glorius, György Gyürky, Michael Heil, Franz Käppeler, Aleksandra Kelic-Heil, Christophor Kozhuharov, Christoph Langer, Tudi Le Bleis, Yuri Litvinov, Gavin Lotay, Justyna Marganiec, Gottfried Münzenberg, Fritz Nolden, Nikolaos Petridis, Ralf Plag, 1 Ulrich Popp, Ganna Rastrepina, René Reifarth, ∗ Björn Riese, Catherine Rigollet, Christoph Scheidenberger, Haik Simon, Kerstin Sonnabend, Markus Steck, Thomas Stöhlker, 11 Tamás Szücs, Klaus Sümmerer, Günter Weber, 11 Helmut Weick, Danyal Winters, Natalya Winters, Philip Woods, and Qiping Zhong GSI-Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany Goethe University Frankfurt, Germany Technische Universität Darmstadt, Germany Technische Universität München, Germany Max-Planck-Institut für Kernphysik, Heidelberg, Germany University of Edinburgh, United Kingdom ATOMKI, Debrecen, Hungary Karlsruher Institut für Technologie, Germany National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan, USA KVI-CART, University of Groningen, The Netherlands Helmholtz-Institut Jena, Jena, Germany This work presents a direct measurement of the Ru(p, γ)Rh cross section via a novel technique using a storage ring, which opens opportunities for reaction measurements on unstable nuclei. A proof-of-principle experiment was performed at the storage ring ESR at GSI in Darmstadt, where circulating Ru ions interacted repeatedly with a hydrogen target. The Ru(p, γ)Rh cross section between 9 and 11 MeV has been determined using two independent normalization methods. As key ingredients in Hauser-Feshbach calculations, the γ-ray strength function as well as the level density model can be pinned down with the measured (p, γ) cross section. Furthermore, the proton optical potential can be optimized after the uncertainties from the γ-ray strength function and the level density have been removed. As a result, a constrained Ru(p, γ)Rh reaction rate over a wide temperature range is recommended for p-process network calculations.