High-resolution laser spectroscopy of long-lived plutonium isotopes

Abstract

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 $5{f}^{6}7{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{7}{F}_{0}\ensuremath{\rightarrow}5{f}^{5}6{d}^{2}7s\phantom{\rule{4pt}{0ex}}(J=1)$ and $5{f}^{6}7{s}^{2}{\phantom{\rule{4pt}{0ex}}}^{7}{F}_{1}\ensuremath{\rightarrow}5{f}^{6}7s7p\phantom{\rule{4pt}{0ex}}(J=2)$ atomic transitions using the HR-RIS method and the hyperfine factors have been extracted for the odd mass nuclei $^{239,241}\mathrm{Pu}$. CLS was performed on the $5{f}^{6}7s{\phantom{\rule{4pt}{0ex}}}^{8}{F}_{1/2}\ensuremath{\rightarrow}J=1/2\phantom{\rule{0.28em}{0ex}}(27\phantom{\rule{0.16em}{0ex}}523.61\phantom{\rule{4.pt}{0ex}}{\text{cm}}^{\ensuremath{-}1})$ ionic transition with the hyperfine $A$ factors measured for $^{239}\mathrm{Pu}$. 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.