Abstract
The shape of the low-energy part of the β-delayed α-particle spectrum of is very sensitive to the αC reduced width of the 7.117 MeV subthreshold state of . This state, in turn, dominates the low-energy p-wave capture amplitude of the astrophysically important (α,γO reaction. The α spectrum following the decay of has been measured by producing a low-energy beam with the TRIUMF isotope separator TISOL, stopping the molecular ions in a foil, and counting the α particles and recoil nuclei in coincidence, in thin surface-barrier detectors. In addition to obtaining the α spectrum, this procedure determines the complete detector response including the low-energy tail. The spectrum, which contains more than events, has been fitted by R- and K-matrix parametrizations which include the measured (α,γO cross section and the measured αC elastic scattering phase shifts. The model space appropriate for these parametrizations has been investigated. For (300), the E1 part of the astrophysical S factor for the (α,γO reaction at =300 keV, values of 79±21 and 82±26 keV b have been derived from the R- and K-matrix fits, respectively.
- Received 16 March 1994
DOI:https://doi.org/10.1103/PhysRevC.50.1194
©1994 American Physical Society