Isotope shifts in dielectronic recombination spectra were studied for Li-like A Nd 57+ ions with A=142 and A=150. From the displacement of resonance positions energy shifts δE 142,150 (2s − 2p 1/2 ) = 40.2(3)(6) meV ((stat)(sys)) and δE 142,150 (2s − 2p 3/2 ) = 42.3(12)(20) meV of 2s − 2p j transitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of 142,150 δ r 2 = -1.36(1)(3) fm 2 . The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.

Beta decay of highly charged ions has attracted much attention in recent years. An obvious motivation for this research is that stellar nucleosynthesis proceeds at high temperatures where the involved atoms are highly ionized. Another important reason is addressing decays of well-defined quantum-mechanical systems, such as one-electron ions where all interactions with other electrons are excluded. The largest modifications of nuclear half-lives with respect to neutral atoms have been observed in beta decay of highly charged ions. These studies can be performed solely at ion storage rings and ion traps, because there high atomic charge states can be preserved for extended periods of time (up to several hours). Currently, all experimental results available in this field originate from experiments at the heavy-ion complex GSI in Darmstadt. There, the fragment separator facility FRS allows the production and separation of exotic, highly charged nuclides, which can then be stored and investigated in the storage ring facility ESR. In this review, we present and discuss in particular two-body beta decays, namely bound-state beta decay and orbital electron capture. Although we focus on experiments conducted at GSI, we will also attempt to provide general requirements common to any other experiment in this context. Finally, we address challenging but not yet performed experiments and we give prospects for the new radioactive beam facilities, such as FAIR in Darmstadt, IMP in Lanzhou and RIKEN in Wako.

For radiative electron capture into the K shell of bare uranium ions, a study of the polarization properties has been performed. For this purpose a position sensitive germanium detector has been used as an efficient Compton polarimeter. This enabled us to measure the degree of linear polarization by analyzing Compton scattering inside the detector and to determine the orientation of the polarization plane. Depending on the observation angle and the beam energy used, the radiation is found to be linearly polarized by up to 80%. In all cases studied, the plane of polarization coincides with the collision plane. The results will be discussed in the context of rigorous relativistic calculations, showing that relativistic effects tend to lead to a depolarization of the radiation emitted. DOI: 10.1103/PhysRevLett.97.223202 PACS numbers: 34.80.Lx, 32.30.Rj, 32.80.Cy, 32.80.Fb Radiative capture of free or quasifree electrons (REC) into high-Z ions has been found to provide a wealth of information on the electron-photon interaction in the presence of strong fields [1,2]. Most important, today, REC is an established tool for studying the time-reversed process, the elementary photoeffect, for one-and few-electron ions at high Z which can otherwise not be addressed in experiments [2]. As a consequence, most properties of the REC were the subject of detailed experimental and theoretical studies (see [2 -5] and references therein). However, a very important aspect of linear polarization so far has not been the subject of experimental investigations although the results of the angular-differential studies already indicate that REC may exhibit distinctive polarization features. Even for the time-reversed process and neutral heavy elements only very few experimental data are available [6,7]. There, the results are strongly affected by electron scattering in the target and except at very high photon energies (above 1 MeV) an unambiguous interpretation of the data is hampered by distortion effects caused by the solid targets used [7]. In contrast, these effects are completely absent in REC studies. Moreover, the polarization features of K-REC radiation have recently attracted particular attention because of its predicted sensitivity to a possible spin polarization of the particles involved in the collision (electrons or ions) [8]. As a consequence, the detection of the linear polarization of K-REC might be applied as an important tool for the control and diagnostics of the degree of the spin polarization of heavy ion beams confined in storage rings. Currently, such a technique is much needed for experiments aiming on a detection of parity nonconservation effects in highly charged ions and for the search of the electric dipole moment of heavy nuclei as proposed for a test of the standard model [9][10][11]. In this context, we like to emphasize that REC into the K shell is the most important charge exchange channel for heavy ions in collisions with light target atoms and, therefore, represents an intense source of radiation.In ...

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to install the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear groundstate properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR can also be used to remove isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases, technical details of the existing ring facility and of the beam requirements at HIE-ISOLDE, together with the cost, time and manpower estimates for the transfer, installation and commissioning of the TSR at ISOLDE are discussed in the present technical design report.

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