High-resolution laser spectroscopy of long-lived plutonium isotopes

Long-lived isotopes of plutonium were studied using two complementary techniques, high-resolution resonance ionization spectroscopy (HR-RIS) and collinear laser spectroscopy (CLS). Isotope shifts have been measured on the 5f67s27F0→5f56d27s(J=1) and 5f67s27F1→5f67s7p(J=2) atomic transitions using the HR-RIS method and the hyperfine factors have been extracted for the odd mass nuclei Pu239,241. CLS was performed on the 5f67s8F1/2→J=1/2(27523.61cm-1) ionic transition with the hyperfine A factors measured for Pu239. Changes in mean-squared charge radii have been extracted and show a good agreement with previous nonoptical methods, with an uncertainty improvement by approximately one order of magnitude. Plutonium represents the heaviest element studied to date using collinear laser spectroscopy.