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New Constraints on the 18 F(p,α) 15 O rate in novae from the (d,p) reaction

1 Tenn. Tech. Univ. 2 ORNL 3 ORAU 4 Ohio Univ. 5 Univ. Of North Carolina 6 Rutgers Univ. 7 Univ. Of Edinburgh 8 Colorado School of Mines 9 Univ. Of Tenn. 10 Dumlupinar Univ. PHYSICAL REVIEW C 71, 032801(R) (2005).

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New Constraints on the 18 F(p,α) 15 O rate in novae from the (d,p) reaction

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  1. 1Tenn. Tech. Univ. 2ORNL 3ORAU 4Ohio Univ. 5Univ. Of North Carolina 6Rutgers Univ. 7Univ. Of Edinburgh 8Colorado School of Mines 9Univ. Of Tenn. 10Dumlupinar Univ. PHYSICAL REVIEW C 71, 032801(R) (2005) New Constraints on the 18F(p,α)15O rate in novae from the (d,p) reaction R.L. Kozub1, D.W. Bardayan2, J.C. Batchelder3, J.C. Blackmon2, C.R. Brune4, A.E. Champagne5, J.A. Cizewski6, T. Davinson7, U. Greife8, C.J. Gross2, C.C. Jewett8, R.J. Livesay8, Z. Ma9, B.H. Moazen1, C.D. Nesaraja1, L. Sahin5,10, J.P. Scott1,2, D. Shapira2, M.S. Smith2, J.S. Thomas6, and P.J. Woods7 The destruction of 18F by proton-induced reactions in novae is shown to be considerably less than recently predicted.

  2. Motivation • 18F has relatively long half-life (~110 min.) • γ rays produced from electron-positron annihilation in β+ decay after expanding nova envelope becomes transparent to 511 keV radiation • Existing and proposed γ-ray observatories should allow measurements of 18F abundance • Information from β+ decay and destruction of 18F ((p,α) , (p, γ)) would provide insight into nova mechanism Dipole Magnet (mass filter) 18F Elab=108.49 MeV I ~ 5 x 105/s Velocity Filters Silicon Detector Array (SIDAR) light, charged particles 118°-157° (8°-27° CM) A=19 detected in coincidence with SIDAR Experiment

  3. Results • Information on 19F from (d,p) reaction gives information on levels in 19Ne (mirror nucleus) • 19Ne is short-lived compound nucleus formed in 18F(p,α)15O reaction Lower rate than predicted Larger 18F abundance in novae Reaction Rate vs. Temperature Shaded Band – present work Dashed Lines - limits set by A. Coc (A. Coc et al., Astron. Astrophys. 357, 561 (2000) SIDAR spectra at 147° (LAB) Energies, spins and parities from D.R. Riley et al., Nucl. Phys. A595, 1 (1995)

  4. Angular Distribution for (d,p) transfer to 6497 keV state in 19F DWBA calculations performed on (d,p) data using parameters from A.W. Barrows, Phys. Rev. 161, 928 (1967) (graph at left) provided good fits It was assumed that 6497 and 6528 keV 3/2+ resonances are isospin mirrors of 8 and 38 keV proton resonances (6419 and 6449 keV excitation) of 19Ne. No evidence in this experiment for 6528 state. If 38 keV resonance had sizable share of l=0 single particle strength, it would dominate reaction 18F(p,α)15O rates calculated using spectroscopic factors as listed in D.R. Tilley et al., for 19Ne resonances not measured

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