High-resolution laser spectroscopy of long-lived plutonium isotopes Voss, Annika; Sonnenschein, Volker; Campbell, P.; Cheal, B.; Kron, T.; Moore, Iain; Pohjalainen, Ilkka; Raeder, S.; Trautmann, N.; Wendt, K.Voss, A., Sonnenschein, V., Campbell, P., Cheal, B., Kron, T., Moore, I., . . . Wendt, K. (2017 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 5f 6 7s 2 7 F 0 → 5f 5 6d 2 7s (J = 1) and 5f 6 7s 2 7 F 1 → 5f 6 7s7p (J = 2) atomic transitions using the HR-RIS method and the hyperfine factors have been extracted for the odd mass nuclei 239,241 Pu. CLS was performed on the 5f 6 7s 8 F 1/2 → J = 1/2 (27 523.61 cm −1 ) ionic transition with the hyperfine A factors measured for 239 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.