Measurement of gamma decay strengths in scandium-41 and carbon-11

The study of the 40Ca(p,#betta#)41Sc reaction was undertaken to measure the antcipated enhancement of the gamma decay widths of states near 7.2 MeV. Seven states, including a state of ambiguous spin which is not a member of the intermediate structure, were examined for capture gamma ray decay to the ground state of 41Sc. The lowest of these states occured at E/sub rho/ = 6.035 MeV and the highest state occured at 6.405 MeV. No gamma decay enhancement was observed. Indeed, only upper limits of approx. 10-3 w.u. for the E1 transitions from the 5/2+ states and approx. 10-2 w.u. for the expected M1 transitions from the intruder state were set. The lack of enhancement may arise either from a cancellation of the transition amplitude due to configuration mixing with collective states of the core of a radial wave function mismatch. The second experiment sought to measure the gamma decay width of the 8.105 MeV state in 11C. This state, if it has a sufficiently large gamma decay width, could influence the stellar nucleosynthesis of 11B and 12C. This state can be populated by the 7Be(α,#betta#)11C reaching by helium burning in red giant stars. This state, along with the 8.424 MeV state, was populated by the 9Be(3He,n)11C* reaction at a bombarding energy of 5.2 MeV. Gamma rays were detected in coincidence with neutrons to determine GAMMA/sub #betta#//GAMMA for these two states. The values determined for GAMMA/sub #betta#//GAMMA were .03 +- .018 and .63 +- .34 for the 8.105 and 8.424 MeV states respectively. These values indicate that the 7Be(α,#betta#)11C reaction rate at red giant temperature is less important in 11B production than previously thought