RUI: Laser Probing of Proton-Rich Rare Isotopes

Augustana University Association, Sioux Falls SD

Investigators

Abstract

This award engages undergraduate students and faculty at Augustana University in Sioux Falls, South Dakota in experimental nuclear physics research. The research will be carried out at Augustana as well as the National Superconducting Cyclotron Laboratory (NSCL) and Facility for Rare Isotope Beams (FRIB) at Michigan State University. Laser spectroscopy will be performed on rare isotopes at NSCL/FRIB to elucidate systematic changes in the shape and size of nuclides with extreme proton-to-neutron ratios. The data will provide vital input to nuclear theories that are used to understand the fundamental forces that bind nuclei together at the edges of stability. Additionally this award, to a primarily undergraduate institution, provides a unique educational experience for students at the forefront of nuclear science. The cutting-edge research and instrumentation that will be funded by this award will continue a tradition at Augustana University to attract and inspire students, an especially important outcome in a geographical area that has traditionally lacked significant research infrastructure. The skills students will gain with precision measurements, such as spectroscopy, are important for the STEM workforce, which is, in turn, a key component of a prosperous and innovative national economy. Collinear laser spectroscopy will be used to study electromagnetic moments and charge radii of proton-rich rare isotopes. Additionally, a high accuracy and high precision laser frequency determination system will be installed at the existing BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/FRIB. The improved laser system will enable studies of nuclear structure effects such as the location of shell closures and nuclear pairing in light mass nuclei. Collinear laser spectroscopy will be performed on rare isotopes, and nuclear charge radii, electromagnetic moments, and nuclear spin of neutron-deficient nuclei will be deduced from atomic hyperfine structure and isotope shifts. Studies of proton-rich 40,41Sc in the vicinity of the proton drip line will reveal if the charge radii of Sc isotopes keeps the decreasing trend across the N = 20 shell closure. These measurements are important for the global and microscopic understanding of the mechanism for the abnormal behavior of charge radii as a function of the proton number around Ca isotopes at the N = 20 shell closure. These data will also be a critical test of a successful Density Functional Theory model using a novel Fayans energy density functional for the Ca chain. The saturated absorption spectrometer will provide a means to determine the probe laser frequency to better than 1 MHz, 10 times more precise than currently achievable using the existing wavelength meter. The greater precision will reduce the systematic errors in the deduced isotope shifts from several percent to much less than one percent. This project is jointly funded by the Experimental Nuclear Physics Program and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.