Studies of the 18F(p,α)15O reaction rate with a 18F beam at the HRIBF

D. W. Bardayan, ORNL Physics Division
J. C. Blackmon, ORNL Physics Division
J. Gómez del Campo, ORNL Physics Division
R. L. Kozub, Tennessee Technological University
J. F. Liang, ORNL Physics Division
Z. Ma, The University of Tennessee, Knoxville
D. Shapira, ORNL Physics Division
M. S. Smith, ORNL Physics Division


The rates of the 18F(p,α)15O and 18F(p,γ)19Ne reactions at T = 0.1-0.4 GK are necessary to understand the emission of positron-annihilation gamma rays expected from novae. Observations of such gamma rays by space-based telescopes would provide direct tests of nova models. These rates, however, are uncertain because of the unknown level structure of 19Ne above the 18F+p threshold. Missing levels in 19Ne were searched for by stopping a 24-MeV 18F beam in a thick polypropylene target, and scattered protons were detected in a silicon-strip detector. The 18F(p,p)18F excitation function has been measured from Ec.m. = 0.3 - 1.3 MeV covering most energies of astrophysical interest, and a significant discrepancy was observed with a recent compilation of 19Ne resonance parameters. © 2004 Elsevier B.V. All rights reserved.