Constraints on the low-energy E-1 cross section of C-12 (alpha, gamma) O-16 from the beta-delayed alpha spectrum of N-16
Aug, 199421 pages
Published in:
- Phys.Rev.C 50 (1994) 1194-1215
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Abstract: (APS)
The shape of the low-energy part of the β-delayed α-particle spectrum of N16 is very sensitive to the α+12C reduced width of the 7.117 MeV subthreshold state of O16. This state, in turn, dominates the low-energy p-wave capture amplitude of the astrophysically important C12(α,γ)16O reaction. The α spectrum following the decay of N16 has been measured by producing a low-energy N1416N+ beam with the TRIUMF isotope separator TISOL, stopping the molecular ions in a foil, and counting the α particles and C12 recoil nuclei in coincidence, in thin surface-barrier detectors. In addition to obtaining the α spectrum, this procedure determines the complete detector response including the low-energy tail. The spectrum, which contains more than 106 events, has been fitted by R- and K-matrix parametrizations which include the measured C12(α,γ)16O cross section and the measured α+12C elastic scattering phase shifts. The model space appropriate for these parametrizations has been investigated. For SE1(300), the E1 part of the astrophysical S factor for the C12(α,γ)16O reaction at Ec.m.=300 keV, values of 79±21 and 82±26 keV b have been derived from the R- and K-matrix fits, respectively.- 27.20.+n
- 23.60.+e
- 95.30.Cq
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