Lifetimes of the astrophysically important states in 19 Ne

1. Lifetimes of the astrophysically important states in 19Ne Wanpeng Tan University of Notre Dame Collaborators: J. Görres, M. Wiescher, J. Daly, M. Couder, A. Couture, H.Y. Lee, E. Stech, E. Strandberg, and C. Ugalde JINA Frontiers 2005

2. Motivation 4U1728-34 Rossi X-ray Timing Explorer Picture: T. Strohmeyer, GSFC • 15O(a,g)19Ne is one of the two routes to break out CNO cycles and trigger rp-process • Energy production • Nucleosynthesis • X-ray bursts: 10-100s, 1039 erg • Superbursts: 1000x stronger and longer Wiescher et al., J. Phys. G 25, R133 (1999) Fisker et al., astro-ph/0410561 (2005) Superburst 4U 1636-53 Picture: T. Strohmayer, GSFC JINA Frontiers 2005

3. Mg (12) Na (11) 13 14 Proton Number Ne (10) F (9) 11 12 O (8) N (7) 9 10 C (6) 15O(a,g)19Ne 3 4 5 6 7 8 18Ne(a,p)21Na 3a process Neutron Number Breakout of the Hot CNO Cycles • T9<0.08 Cold CNO cycles • T9<0.3 Hot CNO cycles • T9>0.3-0.4, breakout leads to the rp-process • Two routes: 15O(a,g)19Ne 18Ne(a,p)21Na JINA Frontiers 2005

4. The importance of 4.03MeV state of 19Ne • Reaction rate of resonances • Three quantities for nuclear physicists to measure: ER, Γγ, Bα besides J • Γγ of α-unbound states of 19Ne are unmeasured. • 4.03 MeV level dominates the rate at temperatures T9 < 0.6. • Very small Bα <4.3x10-4 by Davids et al, PRC2003 • Only upper/lower limits on lifetime τ<50fs by Davidson et al, NPA1973 Γ<440 meV by Hackman et al, PRC2000 ωγfrom Langanke et al, Ap. J. 301, 629(1986) 4.03MeV 4.55MeV 4.71MeV 4.38MeV 4.60MeV T9 JINA Frontiers 2005

5. Doppler-Shift Attenuation Method (DSAM) • Measure lifetime to obtain decay width • Traditional method • Easy to apply and good for poorly resolved peaks • Not sufficient for asymmetric peaks and feeding effects from higher lying states • Full line shape analysis • Realistic Geant4 simulation • Details of the peak shape, especially for double peak structure and tailing effects • Dealing with the feeding from higher lying states γ 19Ne target JINA Frontiers 2005

6. 17O(3He,n-γ)19Ne HPGe • maximize Doppler shift of gamma energies by measuring gammas emitted along the same direction as 19Ne travels. => lifetime measurement • Doppler shifts and geometry uncertainty are cancelled. => energy measurement 45o 3He 3MeV 17O/Ta n det HPGe 135o 3He 3MeV 28.5o 17O/Ta 90o n det JINA Frontiers 2005

7. 19Ne related gamma spectra in coincidence with neutrons 45o 135o 0o • Gamma peaks are not only shifted but also broadened. • Simple DSAM approach is insufficient to study more complicated shapes • Full line-shape analysis is necessary for precise measurements • Details of the peak shape, especially for double peak structure and tailing effects • Dealing with the feeding from higher lying states JINA Frontiers 2005

8. 4034keV state Unshifted Measured Ex = 4034.5±0.8 keV JINA Frontiers 2005

9. 4034keV state of 19Ne 13 fs Best Geant4 fit 2sigma uncertainties Upper limit by Davidson et al 4 fs 29 fs 50 fs Measured lifetime τ= 13±96 fs or Γ=51±4321 meV JINA Frontiers 2005

10. Summary of our results • Errors of mean lifetimes of present work are given at the 95% confidence level. JINA Frontiers 2005