Abstract
Calculation of the thermonuclear (,γ) rate in oxygen-neon nova explosions depends critically upon nuclear structure information for states within ∼600 keV of the threshold in . We have studied the () reaction at 25 MeV using a high-resolution quadrupole-dipole-dipole-dipole magnetic spectrograph. Tritons corresponding to the states () ∼ 6.1–7.1 MeV were observed at ten angles between 10° and 55°. States that were only tentatively identified in past studies have been observed unambiguously. For the first time, we have measured and analyzed angular distributions of the () reaction. We present, also for the first time, a consistent set of experimental spin constraints for all except one of the critical proton-threshold states in . Hydrodynamic nova simulations have been calculated in order to assess the impact on nova nucleosynthesis of remaining uncertainties in values of states and the unknown relevant proton spectroscopic factors. We find that these uncertainties may lead to a factor of up to 20 variation in the (,γ) rate over typical nova peak temperatures, which may then lead to a factor of up to 4 variation in the nova yields of Si-Ar isotopes.
- Received 7 February 2011
DOI:https://doi.org/10.1103/PhysRevC.83.045806
©2011 American Physical Society