Breakup ofHe6incident onBi209near the Coulomb barrier

A neutron-\ensuremath{\alpha}-particle coincidence experiment was performed to study breakup of $^{6}\mathrm{He}$ on a $^{209}\mathrm{Bi}$ target at an incident energy of 22.5 MeV. Direct breakup, as well as breakup through the ${2}^{+}$ excited state of $^{6}\mathrm{He}$ and also the $^{5}\mathrm{He}$$+n$ channel, could be distinguished. A total breakup cross section of $205\ifmmode\pm\else\textpm\fi{}65$ mb was measured. The data compare well with a coupled-channels calculation that assumes a 50% reduction in the B(E1) computed from a pure $^{4}\mathrm{He}$$+2n$ cluster configuration, in agreement with results obtained at much higher energies. A value of $\mathrm{B}(\mathrm{E}2\ensuremath{\Uparrow})=5.4\ifmmode\pm\else\textpm\fi{}0.7{e}^{2}{\mathrm{fm}}^{4}$ is deduced for the ${2}^{+}$ state in $^{6}\mathrm{He}$.