The cross sections and angular correlations for neutron decay into various states in the residual nucleus following the ${}^{10}\mathrm{B}$($e,e^{\text{'}}n$) reaction have been measured over the excitation energy range of 18–33 MeV at an effective momentum transfer of 0.56 fm${}^{-1}$. In the giant resonance, neutron emission leads to the population of two higher excited states in addition to the ground-state transition: 6.97 MeV $7/2^{-}(n_5$) and 11.70 MeV $7/2^{-}+12.06$ MeV $3/2^{-}(n_{6,7}$). This is the first observation of the neutron population of these states. The angular correlations for $n_0$ show a strong forward-backward asymmetry, which suggests interference from a transition with the opposite parity to $E1$. The angular correlations for $n_5$ and $n_{6,7}$ have a peak shift of about ${50}^{°}$ at lower excitation energy and recover above about 24 and 25 MeV for $n_5$ and $n_{6,7}$, respectively. Their patterns are considerably different from that for $n_0$. The angular correlations for each transition were fitted with a Legendre polynomial. The longitudinal-transverse interference coefficient $C_2/A_0$ is negligible for all populations. For $n_0$ decay, all Legendre coefficients $b_i$ are positive, but $b_2$ and $b_3$ for the $n_5$ and $n_{6,7}$ decays are negative at lower excitation energy, and the latter causes a shift of the forward peak. The negative values may come from the signs of the phase differences of $\cos {\delta }_{21}$ and $\cos {\delta }_{20}$. The ${}^{10}\mathrm{B}$($e,e^{\text{'}}n$) cross section measured up to $E_x~32$ MeV agrees well with that of ${}^{10}\mathrm{B}$($\gamma ,n$), except for a peak at 23 MeV of the giant resonance. In comparison with shell-model calculations, the partial cross section for $n_0$ is sizable up to higher excitation energy, and predicted large partial cross sections populating the 6.97 MeV $7/2^{-}$ and 11.70 MeV $7/2^{-}+12.06$ MeV $3/2^{-}$ states in the giant resonance were not observed.

• Received 27 August 2009

DOI:https://doi.org/10.1103/PhysRevC.80.064609