The astrophysically important [Formula Presented] state in [Formula Presented] and the [Formula Presented] stellar rate

D. W. Bardayan, ORNL Physics Division
J. C. Blackmon, ORNL Physics Division
C. R. Brune, The University of North Carolina at Chapel Hill
A. E. Champagne, The University of North Carolina at Chapel Hill
A. A. Chen, Yale University
J. M. Cox, Tennessee Technological University
T. Davinson, The University of Edinburgh
V. Y. Hansper, ORNL Physics Division
M. A. Hofstee, Colorado School of Mines
B. A. Johnson, Tennessee Technological University
R. L. Kozub, Tennessee Technological University
Z. Ma, ORNL Physics Division
P. D. Parker, Yale University
D. E. Pierce, ORNL Physics Division
M. T. Rabban, ORNL Physics Division
A. C. Shotter, The University of Edinburgh
M. S. Smith, ORNL Physics Division
K. B. Swartz, Yale University
D. W. Visser, Yale University
P. J. Woods, The University of Edinburgh


Knowledge of the [Formula Presented] reaction rate is important for understanding stellar explosions, but it was uncertain because the properties of an expected but previously unobserved [Formula Presented] state in [Formula Presented] were not known. This state would provide a strong s-wave resonance for the [Formula Presented] system and, depending on its excitation energy, could dominate the stellar reaction rate at temperatures above 0.2 GK. We have observed this missing [Formula Presented] state by measuring the [Formula Presented] excitation function with a radioactive [Formula Presented] beam at the ORNL Holifield Radioactive Ion Beam Facility (HRIBF). We find that the state lies at a center-of-mass energy of [Formula Presented] keV [Formula Presented] and has a width of [Formula Presented] The measured properties of the resonance are only consistent with a [Formula Presented] assignment. © 2000 The American Physical Society.