Cross Sections and Angular Distributions for the ^<10>B(e, e'n)^9B Reaction in the Giant Resonance Region(I. Nuclear Physics)

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The cross sections and angular correlations for neutron emission to various states in the residual nucleus, following the ^<10>B(e, e'n) reaction, have been measured over the excitation energy range 18-33 MeV at the effective momentum transfer of 0.49 fm^<-1>. In the giant resonance, neutron emission leads predominant population of two higher excited states : (6.97 MeV 7/2^- (n_5), 11.70 MeV 7/2^-+ 12.06 MeV 3/2^- (n_<6, 7>)). This is the first observation for neutron population of these states. The angular distributions for each transition were fitted with Legendre polynomials. The angular distributions for n_0 indicate an interference of a transition with the opposite parity to E1. The angular distributions for n_5 and n_<6, 7> have a peak at about 50°; they are quite different patterns from that for n_0. It might reflect lower E1 amplitude comparing to other multipole ones. It was confirmed that neutron emission from the giant resonance in ^<10>B leaves the residual nucleus ^9B not at the ground state but mainly at 6.97 MeV 7/2^- and 11.70 MeV 7/2^-+ 12.06 MeV 3/2^- states as predicted by shell model calculations with intermediate coupling.
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