Ionization energy of Li 6,7 determined by triple-resonance laser spectroscopy

Rydberg level energies for Li7 were measured using triple-resonance laser excitation, followed by drifted field ionization. In addition to the principal n P2 series, weak Stark mixing from residual electric fields allowed observation of n S2 and hydrogenic Stark manifold series at higher n. Limit analyses for the series yield the spectroscopic ionization energy EI (Li7) =43 487.159 40 (18) cm-1. The Li 6,7 isotope shift (IS) was measured in selected n P2 Rydberg levels and extrapolation to the series limit yields IS (EI) 7,6 =18 067.54 (21) MHz. Results are compared with recent theoretical calculations: EI values from experiment and theory agree to within 0.0011 cm-1, with the remaining discrepancy comparable to uncertainty in QED corrections of order α4 Ry. The difference between experiment and calculated mass-based IS (EI) yields a change in nuclear charge radii between the two isotopes δ r2 7,6 =-0.60 (10) fm2. © 2007 The American Physical Society

Ground-State Electromagnetic Moments of Calcium Isotopes

High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the $^{43-51}$Ca isotopes. The ground state magnetic moments of $^{49,51}$Ca and quadrupole moments of $^{47,49,51}$Ca were measured for the first time, and the $^{51}$Ca ground state spin $I=3/2$ was determined in a model-independent way. Our results provide a critical test of modern nuclear theories based on shell-model calculations using phenomenological as well as microscopic interactions. The results for the neutron-rich isotopes are in excellent agreement with predictions using interactions derived from chiral effective field theory including three-nucleon forces, while lighter isotopes illustrate the presence of particle-hole excitations of the $^{40}$Ca core in their ground state.Comment: Accepted as a Rapid Communication in Physical Review

Nuclear spins, magnetic moments and quadrupole moments of Cu isotopes from N = 28 to N = 46: probes for core polarization effects

Measurements of the ground-state nuclear spins, magnetic and quadrupole moments of the copper isotopes from 61Cu up to 75Cu are reported. The experiments were performed at the 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 56Ni 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 56Ni core and weakening of the Z=28 and N=28 shell gaps.Comment: 13 pagers, 19 figures, accepted by Physical Review

Sympathetic cooling in two-species ion crystals in a Penning trap

We have studied the formation and properties of two-species ion Coulomb crystals in the Penning trap of the SpecTrap experiment. These crystals have been formed by injection of admixture ions from an external source into a previously confined and laser-cooled cloud of magnesium ions. This kind of study, performed over a range of the admixture ions’ charge-to-mass ratios, indicates the conditions for their sympathetic cooling and the formation of two-species ion crystals. This mechanism allows efficient cooling of the admixed species such as highly charged ions which do not feature suitable laser-cooling transitions, and thus make them accessible to high-resolution laser spectroscopy

Collinear laser spectroscopy at ISOLDE:New methods and highlights.

Over three and a half decades of collinear laser spectroscopy and the COLLAPS setup have played a major role in the ISOLDE physics programme. Based on a general experimental principle and diverse approaches towards higher sensitivity, it has provided unique access to basic nuclear properties such as spins, magnetic moments and electric quadrupole moments as well as isotopic variations of nuclear mean square charge radii. While previous methods of outstanding sensitivity were restricted to selected chemical elements with special atomic properties or nuclear decay modes, recent developments have yielded a breakthrough in sensitivity for nuclides in wide mass ranges. These developments include the use of bunched beams from the radiofrequency quadrupole cooler–buncher ISCOOL, which allows a suppression of background by several orders of magnitude. Very recently, the combination of collinear laser spectroscopy with the principle of laser resonance ionisation took shape in the new CRIS setup, providing a very selective and efficient detection of optical resonance. We outline the basic experimental developments and discuss important results on nuclei or chains of isotopes in different mass ranges

Nuclear charge radii of potassium isotopes beyond N = 28

We report on the measurement of optical isotope shifts for 38,39,42,44,46–51K relative to 47K from which changes in the nuclear mean square charge radii across the N = 28 shell closure are deduced. The investigation was carried out by bunched-beam collinear laser spectroscopy at the CERN-ISOLDE radioactive ion-beam facility. Mean square charge radii are now known from 37K to 51K, covering all νf7/2-shell as well as all νp3/2-shell nuclei. These measurements, in conjunction with those of Ca, Cr, Mn and Fe, provide a first insight into the Z dependence of the evolution of nuclear size above the shell closure at N = 28.publisher: Elsevier articletitle: Nuclear charge radii of potassium isotopes beyond journaltitle: Physics Letters B articlelink: http://dx.doi.org/10.1016/j.physletb.2014.02.012 content_type: article copyright: Copyright © 2014 The Authors. Published by Elsevier B.V.status: publishe