High-resolution laser spectroscopy on the hyperfine structure and isotope shift of $$^{237,239}$$Np

Abstract

AbstractNuclear ground state properties of $$^{237,239}$$ 237 , 239 Np were investigated by high-resolution laser spectroscopy at the RISIKO mass separator off-line radioactive beam facility of the University of Mainz. The isotope shifts and the hyperfine parameters were determined in two different atomic ground-state transitions at 398.80 nm and 395.61 nm. The data allowed for calculation of the so far unknown nuclear moments of the short-lived isotope $$^{239}$$ 239 Np, i.e. the nuclear magnetic dipole moment of $$\mu _I$$ μ I = +3.18(2) $$\mu _N$$ μ N and the electric quadrupole moment of $$Q_S$$ Q S  = +4.05(8) eb, using the known nuclear moments of $$^{237}$$ 237 Np as a reference, which were determined by electron paramagnetic resonance and investigations of muonic X-ray hyperfine structures, respectively.