An exclusive measurement has been made of the Coulomb dissociation of the two-neutron halo nucleus ${}^{11}\mathrm{Li}$ at $70\mathrm{MeV}/\mathrm{nucleon}$ at RIKEN. Strong low-energy (soft) $E1$ excitation is observed, peaked at about $E_{\mathrm{x}}=0.6\mathrm{MeV}$ with $B(E1)=1.42(18){\mathrm{e}}^2{\mathrm{fm}}^2$ for $E_{\mathrm{rel}}\le 3\mathrm{MeV}$, which was largely missed in previous measurements. This excitation represents the strongest $E1$ transition ever observed at such low excitation energies. The spectrum is reproduced well by a three-body model with a strong two-neutron correlation, which is further supported by the $E1$ non-energy-weighted cluster sum rule.

Absolute cross sections for isotopically identified products formed in multinucleon transfer in the ${}^{136}\mathrm{Xe}+{}^{198}\mathrm{Pt}$ system at $\sim 8\mathrm{MeV}/\mathrm{nucleon}$ are reported. The isotopic distributions obtained using a large acceptance spectrometer demonstrated the production of the “hard-to-reach” neutron-rich isotopes for $Z<78$ around the $N=126$ shell closure far from stability. The main contribution to the formation of these exotic nuclei is shown to arise in collisions with a small kinetic energy dissipation. The present experimental finding corroborates for the first time recent predictions that multinucleon transfer reactions would be the optimum method to populate and characterize neutron-rich isotopes around $N=126$ which are crucial for understanding both astrophysically relevant processes and the evolution of “magic” numbers far from stability.

Breakup reactions of the one-neutron halo nucleus ${}^{11}\mathrm{Be}$ on lead and carbon targets at about $70\mathrm{MeV}∕\text{nucleon}$ have been investigated at RIKEN by measuring the momentum vectors of the incident ${}^{11}\mathrm{Be}$, outgoing ${}^{10}\mathrm{Be}$, and neutron in coincidence. The relative energy spectra as well as the angular distributions of the ${}^{10}\mathrm{Be}+n$ center of mass system (inelastic angular distributions) have been extracted both for Pb and C targets. For the breakup of ${}^{11}\mathrm{Be}$ on Pb, the selection of forward-scattering angles, corresponding to large impact parameters, is found to be effective to extract almost purely the first-order $E1$ Coulomb breakup component and to exclude the nuclear contribution and higher-order Coulomb breakup components. This angle-selected energy spectrum is thus used to deduce the spectroscopic factor for the ${}^{10}\mathrm{Be}\left(0^{+}\right)\otimes \nu 2s_{1∕2}$ configuration in ${}^{11}\mathrm{Be}$ which is found to be $0.72\pm \mathrm{0.04}$ with a $B\left(E1\right)$ strength up to $E_{\mathrm{x}}=4\mathrm{MeV}$ of $1.05\pm 0.06e^2{\mathrm{fm}}^2$. The energy weighted $E1$ strength up to $E_{\mathrm{x}}=4\mathrm{MeV}$ explains $70\%\pm 10\%$ of the cluster sum rule, consistent with the obtained spectroscopic factor. The non-energy-weighted sum rule within the same energy range is used to extract the root-mean-square distance of the halo neutron to be $5.77\left(16\right)\mathrm{fm}$, consistent with previously known values. In the breakup with the carbon target, we have observed the excitations to the known unbound states in ${}^{11}\mathrm{Be}$ at $E_{\mathrm{x}}=1.78\mathrm{MeV}$ and $E_{\mathrm{x}}=3.41\mathrm{MeV}$. Angular distributions for these states show the diffraction pattern characteristic of $L=2$ transitions, resulting in a $J^{\pi }={(3∕2,5∕2)}^{+}$ assignment for these states. We finally find that even for the C target the $E1$ Coulomb direct breakup mechanism becomes dominant at very forward angles.

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.