| 1. |
- Rodriguez, D., et al.
(författare)
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MATS and LaSpec : High-precision experiments using ion traps and lasers at FAIR
- 2010
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Ingår i: The European physical journal. Special topics. - : Springer Science and Business Media LLC. - 1951-6355 .- 1951-6401. ; 183, s. 1-123
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Forskningsöversikt (refereegranskat)abstract
- Nuclear ground state properties including mass, charge radii, spins and moments can be determined by applying atomic physics techniques such as Penning-trap based mass spectrometry and laser spectroscopy. The MATS and LaSpec setups at the low-energy beamline at FAIR will allow us to extend the knowledge of these properties further into the region far from stability. The mass and its inherent connection with the nuclear binding energy is a fundamental property of a nuclide, a unique ""fingerprint"". Thus, precise mass values are important for a variety of applications, ranging from nuclear-structure studies like the investigation of shell closures and the onset of deformation, tests of nuclear mass models and mass formulas, to tests of the weak interaction and of the Standard Model. The required relative accuracy ranges from 10(-5) to below 10(-8) for radionuclides, which most often have half-lives well below 1 s. Substantial progress in Penning trap mass spectrometry has made this method a prime choice for precision measurements on rare isotopes. The technique has the potential to provide high accuracy and sensitivity even for very short-lived nuclides. Furthermore, ion traps can be used for precision decay studies and offer advantages over existing methods. With MATS (Precision Measurements of very short-lived nuclei using an Advanced Trapping System for highly-charged ions) at FAIR we aim to apply several techniques to very short-lived radionuclides: High-accuracy mass measurements, in-trap conversion electron and alpha spectroscopy, and trap-assisted spectroscopy. The experimental setup of MATS is a unique combination of an electron beam ion trap for charge breeding, ion traps for beam preparation, and a high-precision Penning trap system for mass measurements and decay studies. For the mass measurements, MATS offers both a high accuracy and a high sensitivity. A relative mass uncertainty of 10(-9) can be reached by employing highly-charged ions and a non-destructive Fourier-Transform Ion-Cyclotron-Resonance (FT-ICR) detection technique on single stored ions. This accuracy limit is important for fundamental interaction tests, but also allows for the study of the fine structure of the nuclear mass surface with unprecedented accuracy, whenever required. The use of the FT-ICR technique provides true single ion sensitivity. This is essential to access isotopes that are produced with minimum rates which are very often the most interesting ones. Instead of pushing for highest accuracy, the high charge state of the ions can also be used to reduce the storage time of the ions, hence making measurements on even shorter-lived isotopes possible. Decay studies in ion traps will become possible with MATS. Novel spectroscopic tools for in-trap high-resolution conversion-electron and charged-particle spectroscopy from carrier-free sources will be developed, aiming e. g. at the measurements of quadrupole moments and E0 strengths. With the possibility of both high-accuracy mass measurements of the shortest-lived isotopes and decay studies, the high sensitivity and accuracy potential of MATS is ideally suited for the study of very exotic nuclides that will only be produced at the FAIR facility. Laser spectroscopy of radioactive isotopes and isomers is an efficient and model-independent approach for the determination of nuclear ground and isomeric state properties. Hyperfine structures and isotope shifts in electronic transitions exhibit readily accessible information on the nuclear spin, magnetic dipole and electric quadrupole moments as well as root-mean-square charge radii. The dependencies of the hyperfine splitting and isotope shift on the nuclear moments and mean square nuclear charge radii are well known and the theoretical framework for the extraction of nuclear parameters is well established. These extracted parameters provide fundamental information on the structure of nuclei at the limits of stability. Vital information on both bulk and valence nuclear properties are derived and an exceptional sensitivity to changes in nuclear deformation is achieved. Laser spectroscopy provides the only mechanism for such studies in exotic systems and uniquely facilitates these studies in a model-independent manner. The accuracy of laser-spectroscopic-determined nuclear properties is very high. Requirements concerning production rates are moderate; collinear spectroscopy has been performed with production rates as few as 100 ions per second and laser-desorption resonance ionization mass spectroscopy (combined with beta-delayed neutron detection) has been achieved with rates of only a few atoms per second. This Technical Design Report describes a new Penning trap mass spectrometry setup as well as a number of complementary experimental devices for laser spectroscopy, which will provide a complete system with respect to the physics and isotopes that can be studied. Since MATS and LaSpec require high-quality low-energy beams, the two collaborations have a common beamline to stop the radioactive beam of in-flight produced isotopes and prepare them in a suitable way for transfer to the MATS and LaSpec setups, respectively.
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| 2. |
- Van de Walle, J., et al.
(författare)
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In-trap decay of Mn-61 and Coulomb excitation of Mn-61/Fe-61
- 2009
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Ingår i: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 42:3, s. 401-406
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Konferensbidrag (refereegranskat)abstract
- At ISOL ( Isotope Separator On-Line) facilities, which utilize thick primary production targets, beams of neutron-rich iron isotopes are dificult to obtain due to the long extraction time of these isotopes out of the target matrix. At REX-ISOLDE, an exploratory experiment was carried out to investigate the possibility of producing a post-accelerated beam of neutron-rich iron isotopes by the in-trap decay of neutron-rich manganese isotopes, which are available at ISOLDE using the Resonance Ionization Laser Ion Source (RILIS). This production mechanism was tested for the first time at REX-ISOLDE with an intense and short-lived beam of Mn-61 isotopes. In this work, the proof of principle of this method is demonstrated, although the technical details of the trapping process are currently not well understood and are still under investigation. The first physics results on the Coulomb excitation of Mn-61 and Fe-61 are presented and compared to shell model calculations.
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| 3. |
- Hansen, Klavs, 1958, et al.
(författare)
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Dissociation energies of gold clusters Au+N, N=7-27
- 2006
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Ingår i: Phys. Rev. A. - 1050-2947. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- Unimolecular decay rates and monomer-dimer branching ratios of gold clusters Au (N=7–27) have been measured as a function of excitation energy in photodissociation experiments on size-selected clusters stored in a Penning trap. Part of the data set has previously been used to extract model-free values of dissociation energies [Vogel et al., Phys. Rev. Lett. 87, 013401 (2001)]. Other parts of the data set do not allow this analysis. We use these data to extract tentative dissociation energies, based on the systematics of deviations between an Arrhenius analysis and the model-free values. The observed systematics also allows an estimate of the true frequency factor which often is much higher than the Arrhenius value but in good agreement with the expected detailed balance value. The data are also reanalyzed including radiative cooling which may explain part of the discrepancy between model-free and Arrhenius dissociation-energy values.
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| 4. |
- Hansen, Klavs, 1958, et al.
(författare)
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The dissociation energy of V13+ and the consequences for radiative cooling
- 2005
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Ingår i: Eur. Phys. J. D. - : Springer Science and Business Media LLC. - 1434-6060. ; 34, s. 67-71
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Tidskriftsartikel (refereegranskat)abstract
- The dissociation energy of V13+ has been determined by comparison of the rates of sequential fragmentation, V13+→V 12+→V 11+, and single-step fragmentation of the first fragment, V12+→V 11+. The dissociation-energy value obtained as D=4.35(13) eV has implications for the amount of radiative cooling of the cluster derived form the data presented earlier [C. Walther et al., Phys. Rev. Lett. 83, 3816 (1999)] and is used to analyze additional results.
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| 5. |
- Schweikhard, L., et al.
(författare)
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Cluster studies in ion traps
- 2005
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Ingår i: Proceedings of ISACC 2003. - 1860944957 ; , s. 85-95
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Schweikhard, L., et al.
(författare)
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Photodissociation of Au30+ clusters stored in a Penning trap
- 2005
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Ingår i: Eur. Phys. J. D. - : Springer Science and Business Media LLC. - 1434-6060. ; 36, s. 179-185
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Tidskriftsartikel (refereegranskat)abstract
- Ion trapping allows detailed studies of atomic clusters with various interactions and over a large range of timescales. An overview of methods at hand is given and a specific example is presented in detail where size-selected Au30+ clusters have been stored in a Penning trap and photofragmented by exposure to the third harmonic of a Nd:YAG laser. The resulting mass spectra were sampled after reaction periods varying from 10μs to 1s. The data are used to extract relative dissociation energies, which agree well with model-free values determined previously by other means, albeit with a slightly larger magnitude of the odd-even effect. Below n≃24 the relative dissociation energies extracted from the abundance spectra develop very little over the five orders of magnitude in time covered in the experiments. This behavior has been predicted, but not tested previously. Above n≃24 both spectra and dissociation energies develop odd-even effects after a storage time of 10–100 ms. Possible reasons for this behavior are discussed.
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| 7. |
- Törnqvist, Hans, 1985, et al.
(författare)
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Implementation and evaluation of tilted foils polarization at REX-ISOLDE
- 2012
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Ingår i: Physica Scripta. - 1402-4896 .- 0031-8949. ; T150:T150
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Tidskriftsartikel (refereegranskat)abstract
- The progress within atomic and nuclear physics relies on refining and adding new observables. One of these is the polarization of the nuclear spin, where there is a manifest interest in accessing a wide variety of polarized beams, e. g. at energies suitable for Coulomb excitation and transfer experiments. In particular, exotic nuclei with half-lives considerably less than one second are difficult to produce, but the issues present in traditional methods could be overcome by using the tilted foils technique. Two setups for measuring the degree of polarization of an ion beam after the REX-ISOLDE linear accelerator at CERN are being evaluated. An approach based on Coulomb excitation has been utilized in an experiment and preliminary results will be presented. Furthermore, a beta-NMR setup is currently under construction that will take radioactive beams soon.
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