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With increasing demand for accurate calculation of isotope shifts of atomic systems for fundamental and nuclear structure research, an analytic energy derivative approach is presented in the relativistic coupled-cluster (CC) theory framework to determine the atomic field shift and mass shift (MS) factors. This approach allows the determination of expectation values of atomic operators, overcoming fundamental problems that are present in existing atomic physics methods, i.e. it satisfies the Hellmann–Feynman theorem, does not involve any non-terminating series, and is free from choice of any perturbative parameter. As a proof of concept, the developed analytic response relativistic CC theory has been applied to determine MS and field shift factors for different atomic states of indium. High-precision isotope-shift measurements of ${}^{104-127}$ In were performed in the 246.8 nm (5p ^2 P _3/2 $\to $ 9s ^2 S _1/2 ) and 246.0 nm (5p ^2 P _1/2 $\to $ 8s ^2 S _1/2 ) transitions to test our theoretical results. An excellent agreement between the theoretical and measured values is found, which is known to be challenging in multi-electron atoms. The calculated atomic factors allowed an accurate determination of the nuclear charge radii of the ground and isomeric states of the ${}^{104-127}$ In isotopes, providing an isotone-independent comparison of the absolute charge radii.

The spectroscopic quadrupole moments of the odd–even Mn isotopes between N=28 and N=38 have been measured using bunched-beam collinear laser spectroscopy at ISOLDE, CERN. In order to increase sensitivity to the quadrupole interaction, the measurements have been done using a transition in the ion rather than in the atom, with the additional advantage of better spectroscopic efficiency. Since the chosen transition is from a metastable state, optical pumping in ISOLDE's cooler and buncher (ISCOOL) was used to populate this state. The extracted quadrupole moments are compared to large-scale shell model predictions using three effective interactions, GXPF1A, LNPS and modified A3DA. The inclusion of both the 1νg9/2 and 2νd5/2 orbitals in the model space is shown to be necessary to reproduce the observed increase in the quadrupole deformation from N=36 onwards. Specifically, the inclusion of the 2νd5/2 orbital induces an increase in neutron and proton excitations across the reduced gaps at N=40 and Z=28, leading to an increase in deformation above N=36.

A negative magnetic moment of 23Mg has been determined by collinear laser spectroscopy at CERN-ISOLDE. The absolute value is in agreement with previous measurements by nuclear magnetic resonance while the sign points at high-seniority configurations. The result is consistent with shell-model predictions for nuclei with valence nucleons in the sd shell. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An experimental setup for sensitive high-resolution measurements of hyperfine structure spectra of exotic calcium isotopes has been developed and commissioned at the COLLAPS beam line at ISOLDE, CERN. The technique is based on the radioactive detection of decaying isotopes after optical pumping and state selective neutralization (ROC) (Vermeeren et al 1992 Phys. Rev. Lett.68 1679). The improvements and developments necessary to extend the applicability of the experimental technique to calcium isotopes produced at rates as low as few ions s–1 are discussed. Numerical calculations of laser-ion interaction and ion-beam simulations were explored to obtain the optimum performance of the experimental setup. Among the implemented features are a multi-step optical pumping region for sensitive measurements of isotopes with hyperfine splitting, a high-voltage platform for adequate control of low-energy ion beams and simultaneous β-detection of neutralized and remaining ions. The commissioning of the experimental setup, and the first online results on neutron-rich calcium isotopes are presented. [ABSTRACT FROM AUTHOR]