Structure of 18Ne and the breakout from the hot CNO cycle

K. I. Hahn, Yale University
A. García, University of Washington
E. G. Adelberger, University of Washington
P. V. Magnus, University of Washington
A. D. Bacher, The Indiana University Cyclotron Facility
N. Bateman, Yale University
G. P.A. Berg, The Indiana University Cyclotron Facility
J. C. Blackmon, The University of North Carolina at Chapel Hill
A. E. Champagne, The University of North Carolina at Chapel Hill
B. Davis, University of Notre Dame
A. J. Howard, Yale University
J. Liu, The Indiana University Cyclotron Facility
B. Lund, Yale University
Z. Q. Mao, Princeton University
D. M. Markoff, University of Washington
P. D. Parker, Yale University
M. S. Smith, Yale University
E. J. Stephenson, The Indiana University Cyclotron Facility
K. B. Swartz, University of Washington
S. Utku, Yale University
R. B. Vogelaar, Princeton University
K. Yildiz, Yale University

Abstract

We used the 16O(3He,n)18Ne, 12C(12C,6He)18Ne, and 20Ne(p,t)18Ne reactions to study 18Ne states up to an excitation energy of 10 MeV, with emphasis on levels corresponding to 14O(α,p)17F and 17F(p,γ)18Ne resonances that could strongly affect these reaction rates in hot stellar environments. Excitation energies, widths, absolute cross sections, and angular distributions were measured. We found previously unidentified states at Ex=6.15±0.01 MeV, 7.12±0.02 MeV, 7.35±0.02 MeV, 7.62±0.02 MeV, 8.30±0.02 MeV, (8.45 ±0.03 MeV), 8.55±0.03 MeV, 8.94±0.02 MeV, and 9.58±0.02 MeV. We combined level width, cross section, and angular distribution data to infer Jπ values for a number of the new levels as well as for the previously known 5.1-MeV doublet. Using information from our experiments, we recalculated the 14O(α.p) 17F reaction rate, which constitutes a possible path out of the hot CNO cycle into the rp process and could play an important role in transforming nuclei involved in the hot CNO cycle into heavier nuclei with Z≥10.