Alex MurphyPROCON Proton unbound states in 21 Mg and their astrophysical significance Alex Murphy Nova Herculis 1934: AAT Nova Persei 1901: Herschel X-ray burster in NGC 6624: HST

Alex MurphyPROCON Motivation Better knowledge of the level structure of 21 Mg is needed… Astrophysical Nucleosynthesis and energy generation X-ray bursts Novae Reaction rates dominated by resonant contributions Nuclear Proton-rich nuclei far from stability Large level shifts Comparison of reaction mechanisms Shell model studies The Experiment Resonant scattering reaction: 20 Na(p,p) 20 Na (using TUDA at TRIUMF)

Alex MurphyPROCON Astrophysical motivation Binary systems Compact, evolved star (WD or neutron star) orbiting less evolved massive star (e.g. RG) More massive star expands… Material flows through L1 Material is typically hydrogen Accretion on compact object Layer of H builds up on top of evolved material (e.g. C/O/…) Artist’s conception of accretion from a red giant on to a compact object

Alex MurphyPROCON Astrophysical motivation… Subsequent evolution depends on compact object’s mass and accretion rate. High rate  ‘stable’ H and He burning and mass increase beyond Chandrasekhar: SN 1a Lower accretion rate  cataclysmic variable Neutron star host  X-ray burst White dwarf host  nova Nuclear reactions: explosive hydrogen burning HCNO, rp-process (p,  ), ( ,p) important Material ejected to ISM HEAO light curve of X-ray burst MXB Na(p,  ) 21 Mg reaction significance X-ray bursters: a crucial link in the rp-process Novae: affects NeNa cycle.

Alex MurphyPROCON Astrophysical significance: X-ray Bursters T 9 ~0.4 Energy generation by HCNO cycles Waiting points at 14 O, 15 O and 18 Ne isotopes Unable to generate required energy output 12 C 13 C 13 N 14 N 15 O 16 O 17 F 18 F 18 Ne 15 N 17 O 14 O 15 O 16 O 17 F 18 F 18 Ne 17 O 14 O 15 O 16 O 17 F 18 F 18 Ne 19 Ne 21 Na 22 Na 20 Na 23 Mg 21 Mg 22 Mg 17 O 14 O T 9  0.6 ( ,p) and (p,  ) rates overtake   decays Breakout via rp-process begins (required because of waiting points from). Reaction flow dominated by 15 O( ,  ) 19 Ne(p,  ) 20 Na(p,  ) 21 Na … Triggers subsequent explosion

Alex MurphyPROCON Reaction path in X-ray burster 12 C 13 C 13 N 14 N 15 O 16 O 17 F 18 F 18 Ne 20 Ne 19 Ne 21 Na 22 Na 20 Na 15 N 23 Mg 21 Mg 22 Mg 17 O 14 O T 9 >0.8 Alternative breakout path kicks in Reaction flow dominated by 14 O( ,p) 17 F(p,  ) 18 Ne( ,p) 21 Na…

Alex MurphyPROCON Astrophysical significance: ONeMg Novae Temperatures achieved are too low for breakout NeNa and MgAl cycles thought to provide necessary energy production. NeNa cycle: First stage is 20 Ne(p,  ) 21 Na. Where does the 20 Ne come from?  -decay of 20 Na feeds 20 Ne. Rate of 20 Na(p,  ) compared to the  + decay of 20 Na (448ms) determines abundance of 20 Ne 20 Ne 19 Ne 21 Na 22 Na 20 Na 23 Mg 21 Mg 22 Mg 23 Na NeNa cycle

Alex MurphyPROCON Nuclear significance Specific case Unusual level shifts observed in previous measurements Thomas – Ehrman shift. Breaking of isospin symmetry due to Coulomb induced differences in proton and neutron distributions. Selectivity of 24 Mg( 3 He, 6 He) 21 Mg measurement. could mean there are other states so far unobserved Wider case Few studies on proton rich nuclei in this mass region Level shift in p-rich nuclei Comparison of reaction models our (p,p) vs ( 3 He, 6 He) Shell model… poor performance near drip lines (M. Horoi, private comm.).

Alex MurphyPROCON Previous knowledge of 21 Mg Above proton threshold, only data are Kubono et al. ( NPA 537 (1992) 53) 24 Mg( 3 He, 6 He) 21 Mg

Alex MurphyPROCON Previous knowledge of 21 Mg  E x uncertain to ~15 keV  L from fits to DWBA. J then from comparison with 21 F  Parity by (–1) L  Widths calculated (from Kubono et al., Alburger et al. PRC 23 (1981) 2217 and Wiescher et al. A&A 160 (1986) 56) E x (MeV)E r (MeV)JJ  p (eV) (3/2 +, 5/2 + ) (3/2 +, 5/2 + )3.04x (7/2 + )1.23x (7/2 +,9/2 + )1.58x (1/2 -,3/2 - ) (7/2 + ) (1/2 + ) ?? ??

Alex MurphyPROCON Na(p,p) 20 Na Experimental details  Primary beam: 20  A, 500 MeV, protons  Secondary beam: 20 Na from ISAC  intense sodium beam  surface ion source,  SiC primary target  Currents up to 5x10 7 pps achieved  3.50 < E x ( 21 Mg) < 4.64 MeV  2 energy settings  Target: 795  g/cm2 CH 2 foil  Detectors: 1.5 x LEDA (130° <  cm < 170°) TUDA Thick target method: Scan through region of excitation in 21 Mg to look for resonances.

Alex MurphyPROCON LEDA 800  g/cm 2 CH MeV/u 1.60 MeV/u High sensitivity Faraday cup Recoil proton 9.5 or 13  m Mylar 6 or 9.5  m Mylar 19.5 cm 60.5 cm 4.7 o <  lab < 33.7 o Experimental set-up ~1 epA 20 Na

Alex MurphyPROCON The run: Successful experiment ran in November days of stable 20 Ne calibration beams 7 days of radioactive 20 Na beams: up to 5x10 7 pps. Expect Rutherford + resonances. Resonance depends on E x,  p and L tr Interference Two–body kinematics, low energy loss of protons in target For a selected angle  energy of detected protons reflect the energy the reaction occurred at. Hence, proton spectrum is just an excitation function.

Alex MurphyPROCON Data… Three resonances observed Ex( 21 Mg) = 4.01MeVPrimary aim of the experiment Ex( 21 Mg) = 4.26 MeVPreviously only E x known (no width, spin information) Ex( 21 Mg) = 4.44 MeV (approx)Previously unknown  R-matrix Analysis

Alex MurphyPROCON Other recent data taken with TUDA 21 Na(p,p) 21 Na 22 Na observation in novae 21 Na(p,  ) 22 Mg(  +) 22 Na*(1.275 MeV  -ray) observability in, e.g., INTEGRAL (launched Oct ’02) Synthesis of 22 Na in ONe novae 20 Ne(p,  ) 21 Na(p,  ) 22 Mg(  +) 22 Na or 20 Ne(p,  ) 21 Na(  +) 21 Ne(p,  ) 22 Na Ph.D. Thesis (Edinburgh, 2003) PRC 65 Chris Ruiz et al. (2001) (R)

Alex MurphyPROCON Future directions: Resonant scattering: a powerful technique Requires beam development Limited to states of width > few keV Other channels (p,  ), ( ,p), (d,p)… Many of these are directly of astrophysical significance Maybe used as indirect probes of low cross-section reactions 2 proton unbound states? Facility development Driven by the physics programme Source development Crucial to future programme ECR / Laser ion sources Accelerator development Charge state booster: A < 30  A < 60 ISAC II: up to 6.5 MeV/u, A < 150

Alex MurphyPROCON Many thanks to… M.Aliotta, T.Brown, L.Buchmann, T.Davinson, J.D’Auria, M.Eaton, S.Engel, B.Fulton, D.Groombridge, D.Hunter, D.Hutcheon, A.Laird, J.Pearson, R.Pitkin, I.Robinson, J.Rogers, F.Sarazin, P.Walden, P.Woods Edinburgh TRIUMF York SFU Langara