Speaker
Description
We report on precision measurement of the isotope shifts of neutron-deficient sodium isotopes to determine their nuclear charge radii, with a specific emphasis on $^{21}$Na. Precise determination of the nuclear charge radius allows for accurate calculation of the charge radius difference, ΔR$_{c}$, between $^{21}$Na and its mirror nucleus $^{21}$Ne. This difference provides critical constraints on the nuclear symmetry energy slope, L, and is also correlated with a correction term of the Ft value essential to the unitarity test of the Cabibbo-Kobayashi-Maskawa (CKM) matrix.
We conducted collinear laser spectroscopy (CLS) measurements at the RAON facility using the CLaSsy setup. $^{21}$Na was produced at the ISOL facility using a 70 MeV proton beam from a cyclotron impinging on the SiC target. The $^{21}$Na beam was accelerated to 20 keV and delivered to the CLaSsy beamline as a 10 Hz bunched beam through the Radio Frequency Quadrupole-Cooler Buncher (RFQ-CB). The bunched $^{21}$Na ion beam was neutralized in a charge exchange cell and subsequently interacted with a 589-nm laser beam. Fluorescence light from the D$_{1}$ transition line of $^{21}$Na was detected using a photomultiplier tube (PMT), and its hyperfine spectra were obtained by scanning the voltage applied to the ion beam. Data acquisition was synchronized with the bunched beam to enhance the signal-to-background ratio. Both collinear and anti-collinear methods were employed to enhance ion kinetic energy precision. From these measurements, we achieved improved precision of isotope shifts of $^{21}$Na in determining its nuclear charge radius. This study can be extended to perform precise measurements of nuclear symmetry energy and conduct unitarity tests of the CKM matrix for other isotopes with similar masses.
