Magnetic Dipole Moment ofCu57,59Measured by In-Gas-Cell Laser Spectroscopy

Abstract

In-gas-cell laser spectroscopy study of the 57,59,63,65 Cu isotopes has been performed for the first time using the 244.164 nm optical transition from the atomic ground state of copper. The nuclear magnetic dipole moments for 57,59,65 Cu relative to that of 63 Cu have been extracted. The new value for 57 Cu of µ( 57 Cu) = +2.582(7)µN is in strong disagreement with the previous literature value but in good agreement with recent theoretical and systematic predictions.PACS numbers: 21.10. Ky, 27.40.+z, 27.50.+e, 42.62.Fi With more than 3000 nuclei known so far, the present nuclear chart offers a vast landscape to study mesoscopic systems. Many of these nuclei cannot be described by ab initio calculations and theory uses models based on a fundamental or phenomenological approach in order to describe observables of isotopes yet to discover. The confrontation of experimental data with the theoretical predictions does not only allow for fine tuning of theory but also for discovering new aspects of the interactions at work in the atomic nucleus. This is especially the case when studying isotopes with extreme proton-toneutron ratios. In nuclear structure, the identification of the magic numbers 2, 8, 20, 28, 50, 82, 126 [1] is the foundation for the shell model of the nucleus. While these magic numbers are well established in nuclei close to the valley of β-stability, their universality is strongly questioned [2].Of special interest is the magic number 28 as it is the smallest magic number issued from the spin-orbit interaction added to the nuclear potential. Both the N = 28 isotones [3,4] and the nickel (Z = 28) isotopes [5,6] are under intensive investigation to probe their magic character. With N = Z = 28, 56 Ni is expected to be doubly magic. While it displays a high 2 + 1 excited state in comparison to the other nickel isotopes [5] and a sudden change in the two-neutron and two-proton separation energies [7], both characteristic of a doubly magic nucleus, the evolution of the transition strength B(E2) and the behavior of the nuclei in the vicinity point towards particle excitations across the shell gaps and a breaking of this magic core [8,9,10].The nuclear magnetic dipole moment is a very sensitive tool to study the nuclear structure in the vicinity of magic nuclei.

The on-line low temperature nuclear orientation facility NICOLE

“…Its low value has been seen as suggestive of a possible breaking of the 56 Ni closed shell. However, later measurement of the magnetic moment of 57 Cu (N=28) μ[ 57 Cu]=+2.582(7) μ N [12] was found fully in agreement with the Z=28, N=28 shell closure.…”

Magnetic moment ofAg104mand the hyperfine magnetic field of Ag in Fe using nuclear magnetic resonance o

“…An interesting new method in this respect, viz. in-gas-cell laser spectroscopy [55], was recently reported. This method is currently being applied to the isotopes 97-102 Ag [56].…”

Development of the CRIS (Collinear Resonant Ionisation Spectroscopy) beam line

“…Many optical measurements have been obtained for hundreds of isotopes from the different mass regions of the nuclear chart. Recent highlights in the field have been the measurements made on the halo nuclei 6,8 He [1,2], 8,9,11 Li [3,4] and 7,9,10,11 Be [5], the island of inversion 31,33 Mg [6,7,8,9] and 31 Na [10], the N = 28 shell closure [11,12,13,14,15], the monopole migration of the πf 5/2 orbital in neutron rich Cu [16,17,18,19] and Ga [20,21,22], the rapid onset of deformation in the N = 60 region [23,24] and shape coexistence in the Pb, Po region [25,26]. Developments such as laser ion sources [27,28], target improvements [29] and work at the IGISOL facilty [30] have allowed for a continuous evolution of the field and have significantly improved isotope production over the last few decades.…”