A study of the gamma radiation produced in the alpha-particle bombardment of O 16

Abstract

The excitation function for gamma radiation from the reaction O 16(α, γ)Ne 20 has been studied for laboratory alpha-particle energies E α from 4.8 to 9.9 MeV. Resonances were observed at E α = 5.374, 5.94, 6.61, 6.930, 7.94, 8.17, 8.54 and 9.40 MeV, corresponding to Ne 20 states at excitation energies E x of 9.029, 9.48, 10.02, 10.270, 11.08, 11.27, 11.56, and 12.25 MeV. Gamma-ray angular distribution measurements establish spins and parities of 4 + and 2 + for the 9.029 and 10.270 MeV states, respectively, and indicate that the 11.08 MeV state is probably 4 +. The 2 + assignment for the 10.270 MeV state is supported by the results of triple angular-correlation studies of the gamma-ray cascade through the 1.63 MeV state. Decay schemes have been investigated and estimates made of radiative widths and total widths. It is concluded that the 10.270 MeV state is the first T = 1 state of Ne 20 on the basis of measurements of its excitation energy, spin and parity, total width, and M1 radiative width. The excitation function for 6.13 MeV gamma rays from the reaction O 16(α,α′γ)O 16 has been studied for E α from 8.9 to 9.9 MeV; the data clearly show a resonance at E α = 9.57 MeV corresponding to a state at 12.39 MeV in Ne 20, and there is some evidence for a weaker resonance at E α = 1.25 MeV corresponding to E x = 12.13 MeV.