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Understanding r-process nuclei using the (d,p) reaction on exotic beams

Understanding r-process nuclei using the (d,p) reaction on exotic beams. Kate Jones University of Tennessee. N=50 and N=82 shell closures and the r-process 83 Ge and 85 Se: crossing the N=50 shell closure Shell model calculation of N=51 isotones First data from 132 Sn(d,p).

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Understanding r-process nuclei using the (d,p) reaction on exotic beams

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  1. Understanding r-process nuclei using the (d,p) reaction on exotic beams Kate Jones University of Tennessee • N=50 and N=82 shell closures and the r-process • 83Ge and 85Se: crossing the N=50 shell closure • Shell model calculation of N=51 isotones • First data from 132Sn(d,p) HRIBF Astro Workshop

  2. Important nuclear physics measurements for the r-process HRIBF yields N=82 Neutron magic-number nuclei are most important • Important measurements: • N ~ closed shell • Mass, t1/2 • N = closed shell + 1 • Sn (neutron separation energy) • neutron single-particle structure • (d,p) on closed shell nuclei Close to shell closure Low Q value for (n,g) Low level density Small capture cross section Statistical model not reliable Direct capture important HRIBF Astro Workshop

  3. (d,p) reactions in inverse kinematics Silicon detector p CD2 target (deuteron) 132Sn beam (RIB) 133Sn recoil Recoil Detector Unfavorable kinematics → Reduced Q-value Resolution Rare Ion Beams (RIBs) are difficult and expensive to produce Applicable to all isotopes which can be made into a beam HRIBF Astro Workshop

  4. Crossing N=50: 83Ge and 85Se 2 1/2+ 1 Ex (MeV) 5/2+ 83Ge 85Se 87Kr 89Sr 91Zr ? Possible r-process line N=50 Only known property of 83Ge is t1/2 * ? * Winger, J.A. et al., Phys. Rev. C 38, 285 (1988) from ENSDF www.nndc.bnl.gov HRIBF Astro Workshop

  5. 82Ge(d,p) ΔE (channels) E (channels) IC Se silicon detector array recoil Ge proton TAC Ebeam = 330 MeV (4 MeV/u) 430 μg/cm2 CD2 target counts / 2 ns Ionization chamber at θlab = 0° filled with CF4 SIDAR in lampshade configuration covering θlab = 105°-150° coincidence timing between IC and SIDAR 0 1000 2000 3000 4000 HRIBF Astro Workshop

  6. 83Ge results 105° θlab 127° 149° 0 1200 2400 3600 4800 Ep (keV) ΔEcm≈ 300 keV from the Se doublet Q = 1.47 (0.02 stat., 0.07 sys.) MeV 1st Ex = 280 ( 20 stat.) keV The large width of the first group (ΔEcm≈ 460 keV) and the absence of other levels below Ex = 1 MeV suggest two states. Sn(83Ge) = 3.69 ± 0.07 MeV Δ(83Ge) = – 61.25 ± 0.26 MeV J.S.Thomas PRC 71 (2005) 021302 HRIBF Astro Workshop

  7. 83Ge results cont: Angular distributions 2H(82Ge,p)83Ge Results are consistent with: l = 2 ground state (d5/2) l = 0 1st excited state (s1/2) at Ex=280 keV Spectroscopic Factors Measure single-particle nature of state g.s. S = 0.48 ± 0.14 1st S = 0.50 ± 0.15 HRIBF Astro Workshop

  8. 85Se data 2145.8 2136.8 1444.0 1437.6 1114.9 461.9 0.0 85Se Ex Energy levels from β- decay J.P. Omtvedt, et al., Z. Phys. A 339, 349 (1991). 4 groups are populated, including g.s. and 1st excited Angular distributions show l = 2 ground state and l = 0 1st excited state g.s. S = 0.33 ± 0.09 (d5/2) 1st S = 0.30 ± 0.08 (s1/2) HRIBF Astro Workshop

  9. Shell model calculations: N=51 91Zr 83Ge 85Se 87Kr 89Sr Calculations by D. Dean, 2-body interaction M. Hjorth-Jensen SPE’s from Andres Zucker . HRIBF Astro Workshop

  10. The Neutron-rich tin isotopes 132Sn 124Sn 16O Sb Z = 50 In Stable Doubly magic N = 82 Double shell closure Z=50, N=82 132Sn(d,p) in progress, 130Sn(d,p) to follow HRIBF Astro Workshop

  11. Reaction Calculations CCBA 132Sn(d,p) @ 630MeV By Neil Summers HRIBF Astro Workshop

  12. 132Sn(d,p) detectors Plan View Beam View ORRUBA telescopes ORRUBA telescopes ORRUBA 1000μm 6 x ORRUBA 1000μm 5x5cm2 telescope Beam 5x5cm2 telescopes ORRUBA 1000μm Beam SIDAR ORRUBA telescopes HRIBF Astro Workshop

  13. 132Sn(d,p) photo ORRUBA detectors (back angles) SIDAR detectors (back angles) HRIBF Astro Workshop

  14. 132Sn(d,p) data • Forward telescope 2 • Energy and position from E detector • Calculated energy loss added • E = 63m • TAC gated (MCP downstream) PRELIMINARY Ep(channels) p (channels) HRIBF Astro Workshop

  15. 132Sn(d,p) data + kinematics calculations (11/2-) 3700 (5/2-) 2004.6 1655.7 (1/2-) 1560.9 (9/2-) 853.7 Ep(channels) (3/2-) (7/2-) 0.0 1.45s p1/2? [1] P.Hoff PRL 77(1996)1020 p (channels) HRIBF Astro Workshop

  16. Q-value plot VERY PRELIMINARY g.s EP (channels) Ex HRIBF Astro Workshop

  17. Summary and Comments • N=51 • Completed 82Ge(d,p) and 84Se(d,p) • Measured Sn (mass) for 83Ge • Measured angular distributions • Extracted spectroscopic factors • 132Sn(d,p) • Measurement still in progress • Can see at least 3 previously measured states • See hint of p1/2, should be able to measure in final analysis • 130Sn(d,p) to come! HRIBF Astro Workshop

  18. Collaboration • RIBENS / Center of Excellence collaboration • ORNL D. Bardayan, J. Blackmon, M. Smith, C.Nesaraja, D. Shapira, F. Liang • ORAU M. Johnson • UT KLJ, K. Chae, Z. Ma, B. Moazen • Rutgers University J. Cizewski, S. Pain, R. Hatarik, P.O’Malley • Tennessee Tech Ray Kozub, J.Shriner, S.Paulauskas, J.Howard, D.Sissom • University of Surrey J. Thomas, C.Harlin, N. Patterson • Colorado School of Mines U.Greife, R. Livesay, L.Erikson • Ohio University A. Adekola • Furman A.Gaddis HRIBF Astro Workshop

  19. Shell model calculations: 83Ge 1.5 1.0 Ex (MeV) Calculations from Alex Brown (private communication). Skyrme mean field, adjusted to reproduce the global single particle energies 0.5 1/2+ 5/2+ Expt Theory Calculation of 83Ge [A. Brown, MSU] predicts stronger shell closure than seen in HRIBF 82Ge(d,p)83Ge experiment HRIBF Astro Workshop

  20. N=83 Systematics HRIBF Astro Workshop

  21. (n,) direct capture calculations • G. Arbanas [ORNL] using the code Cupido (F.Dietrich) to calculate direct capture for 88Sr, 84Se and 82Ge • Cupido (F.Dietrich) compared with TEDCA calculations from T. Rausher • Used SF from HRIBF measurements • Koning-Delaroche global optical potential • E1 capture of p-wave neutrons dominates capture cross section into both 83Ge and 85Se. • Semidirect capture through the GDR reduces cross section by ~10% • Results show capture cross sections that are a factor of 10 down from that into 89Sr (stable case) HRIBF Astro Workshop

  22. Reaction Calculations 132Sn(d,p)133Sn[854] By Neil Summers HRIBF Astro Workshop

  23. Nuclear data input into r-process calculations HRIBF Astro Workshop

  24. Other utility of (d,p) reactions - masses r-process waiting point approximation • r-process involves thousands of (n,) reactions • Nuclear masses are needed • to calculate energy released in the r-process • to calculate capture cross sections with a Statistical model • for the “waiting point approximation” used in many r-process calculations • (d,p) reactions can measure masses • Precision adequate for r-process studies • Requires reacceleration HRIBF Astro Workshop

  25. New shell model calculations • New effort by David Dean & M. Hjorth-Jensen to calculate all neutron-rich N=51 nuclei simultaneously • Working with excitations built on a 78Ni core • Cannot currently reproduce measured spacing of 1st excited state energies for n-rich N=51 nuclei • Appears necessary to activate g9/2 protons - which will significantly enlarge model space • Very preliminary results - work in progress HRIBF Astro Workshop

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