Search for excited states in O 25

M. D. Jones, K. Fossez, T. Baumann, P. A. DeYoung, J. E. Finck, N. Frank, A. N. Kuchera, N. Michel, W. Nazarewicz, J. Rotureau, J. K. Smith, S. L. Stephenson, K. Stiefel, M. Thoennessen, R. G.T. Zegers

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Background: Theoretical calculations suggest the presence of low-lying excited states in O25. Previous experimental searches by means of proton knockout on F26 produced no evidence for such excitations. Purpose: We search for excited states in O25 using the O24(d,p)O25 reaction. The theoretical analysis of excited states in unbound O25,27 is based on the configuration interaction approach that accounts for couplings to the scattering continuum. Method: We use invariant-mass spectroscopy to measure neutron-unbound states in O25. For the theoretical approach, we use the complex-energy Gamow Shell Model and Density Matrix Renormalization Group method with a finite-range two-body interaction optimized to the bound states and resonances of O23-26, assuming a core of O22. We predict energies, decay widths, and asymptotic normalization coefficients. Results: Our calculations in a large spdf space predict several low-lying excited states in O25 of positive and negative parity, and we obtain an experimental limit on the relative cross section of a possible Jπ=1/2+ state with respect to the ground state of O25 at σ1/2+/σg.s.=0.25-0.25+1.0. We also discuss how the observation of negative parity states in O25 could guide the search for the low-lying negative parity states in O27. Conclusion: Previous experiments based on the proton knockout of F26 suffered from the low cross sections for the population of excited states in O25 because of low spectroscopic factors. In this respect, neutron transfer reactions carry more promise.

Original languageEnglish (US)
Article number054322
JournalPhysical Review C
Volume96
Issue number5
DOIs
StatePublished - Nov 22 2017

Funding

We would like to thank L. A. Riley for the use of the Ursinus College Liquid Hydrogen Target. This material is based upon work supported by the US Department of Energy, Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-05CH11231 (LBNL) and Awards No. DE-SC0013365 (Michigan State University) and No. DE-SC0008511 (NUCLEI SciDAC-3 collaboration). This work was also supported by Department of Energy National Nuclear Security Administration through the Nuclear Science and Security Consortium under Award No. DE-NA0003180 and by the National Science Foundation under Awards No. PHY14-03906, No. PHY14-04236, No. PHY12-05537, No. PHY11-02511, No. PHY11-01745, No. PHY14-30152, No. PHY09-69058, No. PHY13-06074, and No. PHY12-05357.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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