Measurement of the electric quadrupole moments of 26–29Na

Abstract

The nuclear electric quadrupole moments of the isotopes 26 Na, 27 Na, 28 Na and 29 Na were measured by -NMR spectroscopy in single crystals of LiNbO 3 and NaNO 3 . High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear laser beam. The polarized nuclei were implanted into the crystals and NMR signals were observed in the -decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of 27,31 Na and con rmed the spin I = 3=2 for 31 Na. The results are discussed in comparison with large-basis shell-model calculations.

Onset of intruder ground state in exoticNaisotopes and evolution of theN=20shell gap

“…On the other hand, the quadrupole moment by the SDPF-M is larger by about 30% than the USD value. Recently, a very precise measurement of the quadrupole moments for Na isotopes has been carried out by Keim et al [22,23]. The measured quadrupole moment of 29 Na is 8.6͑3͒ e fm 2 in a good agreement with the SDPF-M prediction, 9.1 e fm 2 .…”

“…As a reference, results from the USD model are presented, also. For the N = 16 and 17 isotopes, the experimental moments [22,23,33] are well reproduced by both the shell-model calculations, reflecting the dominance of the sd-shell configurations in their ground states [see Fig. 1(c)].…”

“…On the other hand, the deviation of the USD result for 29 Na from experiment seems somewhat larger than that for the typical sd-shell nuclei [7]. The situation is almost unchanged if the radial wave function is replaced with the Hartree-Fock one or if the isovector effective charge is tuned [23]. It was thus suspected in Ref.…”

“…1, the electric quadrupole moments and the In (a) and (b), the circles are experimental values taken from Refs. [22,23], while the solid and the dashed lines denote, respectively, the MCSM calculation with the SDPF-M interaction and USDmodel calculation.…”

Perspectives for the VITO beam line at ISOLDE, CERN

“…As a consequence the total population is transferred to magnetic sub-states with higher magnitude of angular momentum. As the laser-atom interaction is a well known process, the polarization can be predicted with relatively good accuracy [22,23]. A major advantage of this method is the high degree of nuclear polarization that can be achieved, typically between 10 % and 80 %, depending on the polarization scheme.…”