[en] The binding energy especially of s-electrons are affected by the finite nuclear size. Isotope shift measurements of electronic transitions provide therefore information about the nuclear charge radius. The sensitivity of the S_1/2→P_1/2 (D1) and the S_1/2 → P_3/2 (D2) transitions in earth alkaline ions to this finite nuclear size effect should be identical apart from a small relativistic contribution, which can be explained with the relativistic admixture of the S_1/2 wave function to the P_1/2 configuration and has been measured for the first time by K. Wendt et al. in Ba⁺. Recent measurements of this effect in Ca⁺ ions have revealed a considerable discrepancy to theoretical predictions. To check whether such a discrepancy is also apparent in the Ba⁺ system, measurements of higher accuracy are required. Therefore, the absolute transition frequencies in several stable barium isotopes have been measured with a collinear/anti-collinear laser spectroscopy approach.

[en] Whenever beams of charged particles are involved in a nuclear physics experiment, also high voltages are involved. In some cases the limited accuracy of high voltage measurements directly spoils the relevance of experimental data. Measuring high voltages with the best-possible accuracy is therefore essential. Collinear laser spectroscopy has become a standard technique for the determination of nuclear charge radii, spins, and magnetic moments. While this technique involves the Doppler shift of the incident laser frequency in the ion's rest frame it is sensitive to the ion velocity and hence, the high voltage applied to accelerate the ions. We want to make use of this feature by determining the high voltage with very high accuracy employing a well-known atomic system and a pump/probe scheme. Accuracies of the order of 1 ppm are feasible. We present the current status of the setup and the results of test measurements with Ca"+ ions.

[en] Collinear laser spectroscopy (CLS) provides the opportunity to extract nuclear charge radii and magnetic dipole as well as electric quadrupole moments in a nuclear-model independent way. CLS utilizes the reduction of velocity spread via acceleration with a DC high-voltage potential of typically a few 10 kV. The isotopes of interest have to exhibit electronic transitions which are accessible with laser systems and sensitive to changes of nuclear charge radii. If these are not available from the ionic ground state, charge exchange can provide access to suitable atomic transitions. We present an updated design of a charge exchange cell for CLS, that can hold acceleration potentials up to 30 kV and operate at temperatures above 430 C to allow for charge exchange with magnesium vapor. The cell is developed in Darmstadt and will be used at Argonne National Laboratory (ANL), where the CAlifornium Rare Isotope Breeder Upgrade (CARIBU) opens up new possibilities for in-flight laser spectroscopy of short lived isotopes, especially in the region beyond the sudden deformation at N=60 and Z>38.

[en] We present recent results of collinear laser spectroscopy measurements on ²¹Mg performed at ISOLDE (CERN). The radioactive Mg ions were produced by 1.4 GeV protons impinging on a SiC target and subsequent selective resonant ionization of the reaction products by a laser ion source. The extracted and mass-separated beam is superimposed with an ultra violet cw laser beam in collinear geometry and optical pumping is performed in a weak magnetic guiding field. If the laser is at resonance with the ionic transition, nuclear spin polarization is created by optical pumping of the hyperfine structure Zeeman levels. After implantation into a suitable crystal an asymmetry in the spatial distribution of the positrons from the β⁺ decay can be observed. Detecting this β-asymmetry while Doppler-tuning the laser wavelength yields the hyperfine structure. High-resolution β-NMR measurements were also performed and the nuclear g-factor was determined. After combining the results of β-asymmetry and β-NMR, also the nuclear spin of ²¹Mg could be extracted. The results are compared to nuclear shell-model predictions, and an outlook to further experiments is given

No abstract available

[en] Many physics experiments depend on accurate high-voltage measurements to determine for example the exact retardation potential of an electron spectrometer as in the KATRIN experiment or the acceleration voltage of the ions at ISOL facilities. Until now only precision high-voltage dividers can be used to measure voltages up to 65 kV with an accuracy of 1 ppm. However, these dividers need frequent calibration and cross-checking and the direct traceability is not given. We report on the status of the ALIVE experiment at the TU Darmstadt which aims to measure high voltages using collinear laser spectroscopy and which has the potential to provide a high-voltage standard and hence, a calibration source for precision high-voltage dividers on the 1 ppm level.

[en] At the TRIGA research reactor at the University of Mainz a collinear laser spectroscopy experiment is currently being installed, which serves as a prototype for the LaSpec collaboration within FAIR at GSI Darmstadt. This setup at the TRIGA reactor allows to study short-lived fission products created near the reactor core by neutron induced fission. A variety of fissionable actinide isotopes are available as target materials up to ²⁴⁹Cf which give access to different regions of the nuclear chart. A special gas-jet transport system will be used to guide the nuclei towards an ion source, where ion beams of a large variety of elements up to refractory elements will be produced and after mass separation be guided either to the collinear beamline of TRIGALASER for laser spectroscopic studies or to TRIGATRAP for high-accuracy mass measurements. In the first phase of the experiment a purely optical detection system with photomultipliers is planned. We present the technical outline of the experiment, the results of ion optics performance tests making use of a surface ion source and give a status report of laser spectroscopy test measurements with Rb atoms.

[en] Ground-state properties of nuclei - spins, magnetic dipole and electric quadrupole moments, and charge radii - provide crucial information on nuclear single-particle and collective behaviour, and are particularly valuable in the context of shell closures and halo effects. They have been studied successfully for many exotic nuclei with the COLLAPS setup located at ISOLDE/CERN, which uses optical excitation or pumping of atoms/ions with laser light together with the hyperfine interaction of the nucleus with the shell electrons, external magnetic fields or electric crystal fields. Recent studies concentrated on light- and medium-mass regions: the quadrupole moment of halo ¹¹Li; spins and magnetic moments of neutron-deficient ²¹Mg around Z=N line and neutron-rich ^31,33Mg inside the 'Island of inversion'; and spins, magnetic and quadrupole moments, and charge radii of neutron-rich Cu isotopes including ^68-72Cu. I present the technique and setup, the physics motivation for the above measurements, as well as the experimental results and their interpretation

[en] We report on the absolute frequency measurement of the 2S-3S two-photon transition of lithium-7 and -6 by employing a frequency comb. The values we obtained in this measurement are a factor ten times better than the last reported ones. We also discuss how a detailed description of the line profile is necessary in order improve the measured values

No abstract available