The probabilities of an excited atomic nucleus to emit particles and rays provide important information on the nuclear level density as well as the -ray strength function. These statistical quantities are important to model nuclear reactions including the complex nucleosynthesis networks that have formed the elements that exist today. But these emission probabilities are hard to come by in the laboratory. The authors demonstrate how they have achieved this challenging task with a new experimental approach, by exciting the stable, doubly magic nucleus Pb in inelastic proton scattering on a hydrogen gas-jet target inside the Experimental Storage Ring (ESR) at the GSI facility, and by detecting the lead (Pb) beamlike ions instead of the emitted rays or neutrons. Such measurements in inverse kinematics in a storage ring are free from complications by, e.g., competing reactions or energy loss in a fixed target. Here, the Pb beam passes the low-density hydrogen target a million times per second, restoring the luminosity in the regime of the thin target that preserves pristine excitation-energy resolution and particle identification capability, and enables outstanding detection efficiencies. The present results along with improvements under development promise future results for many short-lived nuclei of interest in astrophysics and nuclear science applications.
