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We report the first confirmation of the predicted inversion between the 2p 3=2 and 1f 5=2 nuclear states in the g 9=2 midshell. This was achieved at the ISOLDE facility, by using a combination of insource laser spectroscopy and collinear laser spectroscopy on the ground states of 71;73;75 Cu, which measured the nuclear spin and magnetic moments. Much of the current effort in nuclear physics is focused on determining how the nuclear shell structure is changing in neutron-rich nuclei. This has been triggered by the observation of unexpected phenomena in several neutronrich isotopes, since radioactive ion beams of such nuclei became available more than three decades ago. In the lighter elements (e.g., He, Li, Be), neutron halos and skins were observed. Around the neutron-rich 32 Mg region an ''island of inversion'' was discovered. In the neutron-rich region towards doubly magic 78 Ni, a sudden drop in the position of the first excited 5=2 À state in 71;73 Cu isotopes was observed more than a decade ago [1]. The lowering of the 5=2 À energy from above 1 MeV in 69 Cu to 166 keV in 73 Cu suggested that this state might become the ground state in 75 Cu. The migration of this level, associated with the occupation of the 1f 5=2 single-particle orbital, was attributed to a strong attractive monopole interaction that becomes active when neutrons occupy the 1g 9=2 orbital [2]. Such monopole interactions exist also in near-stable nuclei, but their impact on the evolution of shell structure and shell gaps in far-from-stability nuclei remained unnoticed until recently [3]. Also in other neutron-rich regions dramatic monopole shifts were observed when valence neutrons and protons are occupying orbits having their orbital and spin angular momentum, respectively, aligned and antialigned. It is now understood that one of the physics mechanisms driving these monopole shifts is the tensor part of the residual nucleon-nucleon interaction [4]. A steep lowering of the 1=2 À level from about 1 MeV in 69 Cu down to 135 keV in 73 Cu has also been observed [5,6]. Thus this level is also a potential ground-state candidate in 75 Cu. While most shell-model interactions do reproduce a lowering of the 5=2 À level and predict an inversion with the normal 3=2 À ground state somewhere between 73 Cu and 79 Cu [4,[7][8][9][10], none of them reproduce the lowering of the 1=2 À state. Some significant physics mechanism is either omitted or seriously underestimated in each of the recently developed shell-model interactions. Therefore, experimental establishment of ground-and excited-state nuclear spins and the properties of their wave function (through spectroscopic factors, magnetic moments, transition moments, etc.) is a crucial step in PRL 103,

Abstract. Collinear laser spectroscopy experiments with the Sc + transition 3d4s 3 D 2 → 3d4p 3 F 3 at λ = 363.1 nm were performed on the 42−46 Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac-Fock calculations were performed in order to evaluate the specific mass-shift, M SMS , and field-shift, F , parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean square charge radii of the isomeric states relative to the ground states for 44 Sc and 45 Sc were also extracted. The charge radii difference between the ground and isomeric states of 45 Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

Measurements of the ground-state nuclear spins and magnetic and quadrupole moments of the copper isotopes from 61 Cu up to 75 Cu are reported. The experiments were performed at the CERN online isotope mass separator (ISOLDE) facility, using the technique of collinear laser spectroscopy. The trend in the magnetic moments between the N = 28 and N = 50 shell closures is reasonably reproduced by large-scale shell-model calculations starting from a 56 Ni core. The quadrupole moments reveal a strong polarization of the underlying Ni core when the neutron shell is opened, which is, however, strongly reduced at N = 40 due to the parity change between the pf and g orbits. No enhanced core polarization is seen beyond N = 40. Deviations between measured and calculated moments are attributed to the softness of the 56 Ni core and weakening of the Z = 28 and N = 28 shell gaps.

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