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Kyung Yuk Chae University of Tennessee, Knoxville / ORNL

First Experimental Constraints on the interference of 3/2 + resonances in the 18 F(p, a ) 15 O reaction. Kyung Yuk Chae University of Tennessee, Knoxville / ORNL. 18 F(p, a ) 15 O reaction. INTEGRAL. 511 keV (and below). 17 O(p, g ) 17 F(p, g ) 18 Ne(e + n e ). (p, a ) 15 O

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Kyung Yuk Chae University of Tennessee, Knoxville / ORNL

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  1. First Experimental Constraints on the interference of 3/2+ resonances in the 18F(p,a)15O reaction Kyung Yuk Chae University of Tennessee, Knoxville / ORNL HRIBF Workshop, ORNL

  2. 18F(p,a)15O reaction INTEGRAL 511 keV (and below) 17O(p,g) 17F(p,g)18Ne(e+ne) (p,a)15O (p,g)19Ne 18F 18F t ~ 2hrs, large production rate Important positron annihilation source HRIBF Workshop, ORNL

  3. Previous Studies [Cos95, Reh96, Utk98, Bar00, Gra00, Bar01, Bar02, Bar04, deS05, Koz05] • (p,p) and (p,a) reactions with stable and exotic beams • No study on interference effects among lower-lying 3/2+ resonances Measuring cross sections off resonance is required Séréville et. al. HRIBF Workshop, ORNL

  4. Experimental Setup • ~10518F/sec, 18F/18O ~0.04 • 70 mg/cm2 CH2 • Energy steps of 1 MeV (Elab) 29o ≤ qlab ≤ 73o (SIDAR) 11.5o ≤ qlab ≤ 22.5o (MINI) MINI SIDAR HRIBF Workshop, ORNL

  5. Particle Identification I 18O(p,a)15N 18F(p,a)15O a Energy (arbitrary) Heavy Recoil Energy (arbitrary) HRIBF Workshop, ORNL

  6. Particle Identification II 18F/18O 18O 18O(p,a)15N 18O(p,a)15N SIDAR strip number Background 18F(p,a)15O Total Energy (arbitrary) HRIBF Workshop, ORNL

  7. Differential Cross Section cross section Christensen et. al. upper limit HRIBF Workshop, ORNL

  8. Results Jp= 3/2+ levels: 8-, 38-, and 665-keV (eight possibilities) 4out of8possibilities are ruled-out First experimental constraints on the interference Phys. Rev. C 74 012802(R) HRIBF Workshop, ORNL

  9. S-factors & Reaction Rates uncertainty is reduced by up to 37% in nova temp. Measurements of the cross section between 330- and 665 keV HRIBF Workshop, ORNL

  10. Conclusion • element synthesis calculations • (Computational Infrastructure • for Nuclear Astrophysics) • 169 isotopes up to 54Cr • REACLIB database • 1.35 Msun ONeMg white dwarf • 28 zones Factor of 2 variation in 18F abundance HRIBF Workshop, ORNL

  11. Thank You K.Y. Chae, M.W. Gudiry, Z. Ma, C.D. Nesaraja D.W. Bardayan, J.C. Blackmon, M.S. Smith D. Gregory, R.L. Kozub, S. Paulauskas, J.F. Shriner Jr., N. Smith M.S. Johnson R.J. Livesay, M. Porter-Peden S.D. Pain, J.S. Thomas UTK/ORNL ORNL TTU ORAU CSM Rutgers HRIBF Workshop, ORNL

  12. Appendix

  13. Novae & g-ray - Isotopic abundances - Expanding shell properties - Galactic distribution of novae - Mixing/Convection mechanisms Nova Cygni 1992 - Abundant - Not absorbed 511 keV line & continuum model HRIBF Workshop, ORNL

  14. 18F in novae Hot CNO cycle: 12C(p,g)13N(p,g)14O(e+ne)14N(p,g)15O(e+ne)15N(p,a)12C T ~ 108 K At higher temperatures 14O(a,p)17F(p,g)18Ne(e+ne)18F OR 16O(p,g)17F(p,g)18Ne(e+ne)18F cf. CNO cycle: HRIBF Workshop, ORNL

  15. Beam Production & Delivery HRIBF Workshop, ORNL

  16. counts E (channel) Beam Current MINI Ion Counter elastic 18F+18O 18F DE (channel) 18O E (channel) HRIBF Workshop, ORNL

  17. Resonance Parameters HRIBF Workshop, ORNL

  18. Summary • 1H(18F,a)15O cross section measurements (Ec.m.=663-887 keV) at ORNL HRIBF • 1H(18O,a)15N measurements • 4 out of 8 possibilities are ruled-out • First experimental constraints on the interference effects • Uncertainty in the reaction rate at nova temperature is reducedby up to 37% • Element synthesis calculations (a factor of 2 variation in the amount of 18F) HRIBF Workshop, ORNL

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