Coulomb Dissociation ofC19and its Halo Structure
The extremely neutron-rich nucleus ${}^{19}\mathrm{C}$ has been studied by Coulomb dissociation into ${}^{18}\mathrm{C}+n$ at $67A\mathrm{MeV}$. A large $E1$ strength of $0.71\ifmmode\pm\else\textpm\fi{}0.07{e}^{2}\mathrm{fm}{}^{2}$ has been observed at low excitation energies. An analysis of the angular distribution of ${}^{18}\mathrm{C}+n$ center of mass has led to a determination of the neutron separation energy of ${}^{19}\mathrm{C}$ to be $530\ifmmode\pm\else\textpm\fi{}130\mathrm{keV}$. The $E1$ strength distribution can be well reproduced for a ${}^{19}\mathrm{C}$ ground state structure with a dominant $s$-wave valence neutron, providing a consistent picture of the neutron halo structure of ${}^{19}\mathrm{C}$.