Spectroscopy of He-7 states using the (N-15, F-17) reaction on Be-9 - art.no. 024312

We have studied states of He-7 using the Be-9(N-15,F-17)He-7 reaction at tw o incident energies, E-lab = 240 MeV and 318.5 MeV and observed clearly the first excited state of He-7. An extended study of the three-body backgroun d was required to determine the excitation energy and width. The resonance parameters obtained for l=1 are E-x=2.95(10) MeV, and Gamma =1.9(3) MeV. Th ere is also evidence of a broad excited state at E-x =5.8(3) MeV with Gamma =4(1) MeV. From the analysis of the He-7 ground state resonance, we extrac ted a value of 0.14(2) MeV for the width. In the calibration reaction C-12( N-15,F-17)Be-10 three high-lying states of Be-10 are found at 13.6(1), 15.3 (2), and 16.9(2) MeV.