Direct mass measurements of 19B, 22C, 29F, 31Ne, 34Na and other light exotic nuclei

Abstract

We report on direct time-of-flight based mass measurements of 16 light neutron-rich nuclei. These include the first determination of the masses of the Borromean drip-line nuclei ${}^{19}$B, ${}^{22}$C and ${}^{29}$F as well as that of ${}^{34}$Na. In addition, the most precise determinations to date for ${}^{23}$N and ${}^{31}$Ne are reported. Coupled with recent interaction cross-section measurements, the present results support the occurrence of a two-neutron halo in ${}^{22}$C, with a dominant $\nu 2s_{1/2}^2$ configuration, and a single-neutron halo in ${}^{31}$Ne with the valence neutron occupying predominantly the 2$p_{3/2}$ orbital. Despite a very low two-neutron separation energy the development of a halo in ${}^{19}$B is hindered by the 1$d_{5/2}^2$ character of the valence neutrons.

5 pages