The ground state and several excited states of 9 He, the most neutron-rich nucleus to date, have been identified by means of the reaction 9 Be(/r~,/r + ) 9 He. The mass excess of the ground state has been measured and it is found that the nucleus is unbound against single-neutron decay by 1.13 ±0.10 MeV only. It is found that the excited-state spectrum of this nucleus, which is very far from the valley of stability, is in good agreement with the predictions of "no-core" shell-model calculations whose parameters were optimized for the stable nuclei in the valley.

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The first angular distributions for pion double charge exchange to discrete nuclear states are reported. The analog and nonanalog states are found to be equally strongly populated. The direct, surface-dominated nature of the reaction is clearly demonstrated by the angular distribution shapes. It is shown that in order to produce detailed agreement with the data, the present ideas for the pion charge-exchange form factors may need to be drastically revised.

Precision measurements of the analyzing powers for the reaction p pol +p ^d + ir + have been made at ^550, 600, 650, 700, and 800 MeV. The data have been analyzed in terms of Legendre polynomials. It is found that excitation functions for both even and odd Legendre coefficients exhibit very similar resonant behaviors. It is concluded that the triplet amplitudes are as strongly dominated by the A(1232) as the well-known singlet amplitude, l D 2 , and that the data do not exhibit any anomalous behavior suggestive of dibaryon resonances.

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