Spectroscopic quadrupole moment of 23Na from muonic X-rays☆

Abstract With the crystal spectrometer at muon channel I at SIN we measured the 3 d 5 2 −2 p 3 2 transition in muonic 23 Na. The h.f.s. of the 2 p 3 2 level was resolved and the spectroscopic quadrupole moment of the nuclear ground state determined: Q = 0.1006 ± 0.0020 b. Using a collective particle-rotor model description of 23 Na which includes small ΔK = 1 admixtures in the wave functions, we find agreement between our measured spectroscopic quadrupole moment and the one derived from measured B (E2) values. Combining the quadrupole moment Q with the quadrupole coupling constant measured in the electronic atom of 23 Na, we derive the electric field gradient at the nucleus for two different electronic states: 〈d E /d z 〉 = 0.1185(32) ea −3 0 for the 3 2 P 3 2 state, 〈d E /d z 〉 = 0.0410(27) ea −3 0 for the 4 2 P 3 2 state. The field gradient for the 3 2 P 3 2 state is compared with recent many-body calculations of the hyperfine interaction in alkali atoms.