Speaker
Description
The physics program at the Oslo Cyclotron Laboratory (OCL) pursues experimental studies of statistical properties of highly excited atomic nuclei using the Oslo Scintillator Array (OSCAR). The thirty large-volume (3.5” × 8”) LaBr3:Ce detectors of OSCAR are coupled to an array of segmented silicon telescope detectors to detect particle-gamma coincidences following light-ion induced nuclear reactions. These measurements produce gamma-ray spectra as a function of excitation energy. Primary gamma-ray spectra are extracted with a subtraction algorithm and decomposed into the nuclear level density and the gamma-ray strength function - a procedure that has become known as the “Oslo method”. The experiments probe resonant structures on the low-energy tail of the giant dipole resonance, including the pygmy dipole resonance, the scissors resonance, and the low-energy enhancement. Systematic studies reveal how these resonances evolve with nuclear deformation and neutron excess. Experimental level densities and gamma-ray strength functions can furthermore be used to constrain neutron-capture cross sections in Hauser-Feshbach calculations. This method provides experimentally constrained capture cross sections also for cases where direct measurements with neutrons are not possible, for example for branch points in the astrophysical s-process. Recent results from studies performed at OCL will be presented, together with prospects for future OSCAR experiments both at OCL and other laboratories.