Using symmetric ${}^{112}\mathrm{S}\mathrm{n}+{}^{112}\mathrm{S}\mathrm{n}$, ${}^{124}\mathrm{S}\mathrm{n}+{}^{124}\mathrm{S}\mathrm{n}$ collisions as references, we probe isospin diffusion in peripheral asymmetric ${}^{112}\mathrm{S}\mathrm{n}+{}^{124}\mathrm{S}\mathrm{n}$, ${}^{124}\mathrm{S}\mathrm{n}+{}^{112}\mathrm{S}\mathrm{n}$ systems at an incident energy of $E/A=50\mathrm{M}\mathrm{e}\mathrm{V}$. Isoscaling analyses imply that the quasiprojectile and quasitarget in these collisions do not achieve isospin equilibrium, permitting an assessment of isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state. DOI: http://dx.doi.org/10.1103/PhysRevLett.92.062701 © 2004 The American Physical Society

Isotopic distributions for light particles and intermediate mass fragments have been measured for ${}^{112}\mathrm{Sn}{+}^{112}\mathrm{Sn}$, ${}^{112}\mathrm{Sn}{+}^{124}\mathrm{Sn}$, ${}^{124}\mathrm{Sn}{+}^{112}\mathrm{Sn}$, and ${}^{124}\mathrm{Sn}{+}^{124}\mathrm{Sn}$ collisions at $E/A=50\mathrm{}\mathrm{MeV}$. Isotope, isotone, and isobar yield ratios are utilized to estimate the isotopic composition of the gas phase at freeze-out. Analyses within the equilibrium limit imply that the gas phase is enriched in neutrons relative to the liquid phase represented by bound nuclei. These observations suggest that neutron diffusion is commensurate with or more rapid than fragment production.

Partial cross sections and corresponding momentum distributions have been studied in the one-neutron knockout reaction ( ${}^{12}\mathrm{Be}{,}^{11}\mathrm{Be}+\gamma$) on a ${}^9\mathrm{Be}$ target at 78 MeV/nucleon. The resulting spectroscopic factors for the only two bound states of ${}^{11}\mathrm{Be}$ are $0.42\pm 0.06$ ( $1/2^{+}$) and $0.37\pm 0.06$ ( $1/2^{-}$), where the errors are experimental only. This result shows that $N=8\mathrm{}$ is not a good closed shell in the neutron-rich ${}^{12}\mathrm{Be}$ and that the last neutron pair is two-thirds in the ( ${1s}^2{+0d}^2$) intruder configuration.

The production of pions and kaons has been measured in ${}^{197}\mathrm{Au}{+}^{197}\mathrm{Au}$ collisions at beam energies from 0.6 to $1.5A\mathrm{GeV}$ with the kaon spectrometer at SIS/GSI. The $K^{+}$ meson multiplicity per nucleon is enhanced in $\mathrm{Au}+\mathrm{Au}$ collisions by factors up to 6 relative to $\mathrm{C}+\mathrm{C}$ reactions, whereas the corresponding pion ratio is reduced. The ratio of the $K^{+}$ meson excitation functions for $\mathrm{Au}+\mathrm{Au}$ and $\mathrm{C}+\mathrm{C}$ collisions increases with decreasing beam energy. This behavior is expected for a soft nuclear equation-of-state.

The $E1$ strength distribution in ${}^{68}\mathrm{Ni}$ has been investigated using Coulomb excitation in inverse kinematics at the $\mathrm{R}{}^3\mathrm{B}\mathrm{\text{−}}\mathrm{LAND}$ setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess.

Proton and ion beams open up new vistas for the curative treatment of tumors, but adequate technologies for monitoring the compliance of dose delivery with treatment plans in real time are still missing. Range assessment, meaning the monitoring of therapy-particle ranges in tissue during dose delivery (treatment), is a continuous challenge considered a key for tapping the full potential of particle therapies. In this context the paper introduces an unconventional concept of range assessment by prompt-gamma timing (PGT), which is based on an elementary physical effect not considered so far: therapy particles penetrating tissue move very fast, but still need a finite transit time--about 1-2 ns in case of protons with a 5-20 cm range--from entering the patient's body until stopping in the target volume. The transit time increases with the particle range. This causes measurable effects in PGT spectra, usable for range verification. The concept was verified by proton irradiation experiments at the AGOR cyclotron, KVI-CART, University of Groningen. Based on the presented kinematical relations, we describe model calculations that very precisely reproduce the experimental results. As the clinical treatment conditions entail measurement constraints (e.g. limited treatment time), we propose a setup, based on clinical irradiation conditions, capable of determining proton range deviations within a few seconds of irradiation, thus allowing for a fast safety survey. Range variations of 2 mm are expected to be clearly detectable.