Abstract Page

The astrophysically important 3⁺ state in ¹⁸Ne and the ¹⁷F(p,gamma)¹⁸Ne stellar rate

D. W. Bardayan,^1,2 J. C. Blackmon,¹ C. R. Brune,³ A. E. Champagne,³ A. A. Chen,² J. M. Cox,⁴ T. Davinson,⁵ V. Y. Hansper,^1,3 M. A. Hofstee,⁶ B. A. Johnson,⁴ R. L. Kozub,⁴ Z. Ma,^1,7,8 P. D. Parker,² D. E. Pierce,¹ M. T. Rabban,¹ A. C. Shotter,⁵ M. S. Smith,¹ K. B. Swartz,² D. W. Visser,² and P. J. Woods⁵

¹Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
²A. W. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520-8124
³Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599
⁴Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505
⁵Department of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
⁶Department of Physics, Colorado School of Mines, Golden, Colorado 80401
⁷Chinese Institute for Atomic Energy, Beijing 102413, People's Republic of China
⁸Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831

Phys. Rev. C62 (2000) 055804

Knowledge of the ¹⁷F(p,gamma)¹⁸Ne reaction rate is important for understanding stellar explosions, but it was uncertain because the properties of an expected but previously unobserved 3⁺ state in ¹⁸Ne were not known. This state would provide a strong s-wave resonance for the ¹⁷F + p system and, depending on its excitation energy, could dominate the stellar reaction rate at temperatures above 0.2 GK. We have observed this missing 3⁺ state by measuring the ¹H(¹⁷F,p)¹⁷F excitation function with a radioactive ¹⁷F beam at the ORNL Holifield Radioactive Ion Beam Facility (HRIBF). We find that the state lies at a center-of-mass energy of E_r = 599.8±1.5_stat±2.0_sys keV ] (E_x = 4523.7±2.9 keV) and has a width of Gamma= 18±2_stat±1_sys keV. The measured properties of the resonance are only consistent with a J^pi = 3⁺ assignment.

Observation of the Astrophysically Important 3⁺ State in ¹⁸Ne via Elastic Scattering of a Radioactive ¹⁷F Beam from ¹H

D. W. Bardayan^1,2, J. C. Blackmon¹, C. R. Brune³, A. E. Champagne³, A. A. Chen², J. M. Cox⁴, T. Davinson⁵, V. Y. Hansper^1,3, M. A. Hofstee⁶, B. A. Johnson⁴, R. L. Kozub⁴, Z. Ma^1,7,8, P. D. Parker², D. E. Pierce¹, M. T. Rabban¹, A. C. Shotter⁵, M. S. Smith¹, K. B. Swartz², D. W. Visser², and P. J. Woods⁵

¹Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831

²A. W. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06511

³Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599

⁴Physics Department, Tennessee Technological University, Cookeville, Tennessee 38505

⁵Department of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom

⁶Department of Physics, Colorado School of Mines, Golden, Colorado 80401

⁷Chinese Institute for Atomic Energy, Beijing, 102413, People's Republic of China

⁸Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831

The ¹⁷F(p, gamma)¹⁸Ne reaction is important in stellar explosions, but its rate has been uncertain because of an expected 3⁺ state in ¹⁸Ne that has never been conclusively observed. This state would provide a strong l = 0 resonance and, depending on its excitation energy, could dominate the stellar reaction rate. We have observed this missing 3⁺ state by measuring the ¹H(¹⁷F,p) ¹⁷F excitation function with a radioactive ¹⁷F beam at the ORNL Holifield Radioactive Ion Beam Facility. We find that the state lies at a center-of-mass energy of E_r = 599.8±1.5_stat ±2.0_sys keV ( E_x = 4523.7±2.9 keV) and has a width of Gamma= 18±2 _stat±1_sys keV.