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News Archive 2009

18.12.09: Article selected for Virtual Journal of Applications of Superconductivity
A recently in Rev. Sci. Instrum. published article about the quality factor of a superconducting rf resonator in a magnetic field has been selected for the December 15, 2009 issue of Virtual Journal of Applications of Superconductivity external Link. This selection for the Virtual Journal is an appreciation for our important frontier research.
The article reports the investigation of the quality factor of a superconducting NbTi resonator at 1.6 MHz in a magnetic field up to 1.2 T as well as its temperature dependence. An optimization procedure for the quality factor is presented and the relevance of the Q-value degeneration due to the superconducting magnetoresistance is discussed with respect to real trap experiments. Read more in the article ... >
22.10.09: Nuclear Spins and Magnetic Moments of 71,73,75Cu: Inversion of π2p3/2 and π1f5/2 Levels in 75Cu
In a recently published Physical Review Letters article K. T. Flanagan et al. report the first confirmation of the predicted inversion between the π2p3/2 and π1f5/2 nuclear states in the νg9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of insource laser spectroscopy and high-resolution collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained precision values are μ(71Cu) = + 2.2747(8)μN, μ(73Cu) = + 1.7426(8)μN, and μ(75Cu) = + 1.0062(13)μN corresponding to spins I = 3/2 for 71,73Cu and I = 5/2 for 75Cu. Read more in the article ... >
25.09.09: MATS & LaSpec Technical Design Report finalized
The FAIR Collaborations MATS and LASPEC have finalized their common Technical Design Report. The report demonstrates the advanced status of these experiments and is available at the homepage of the MATS collaboration external Link.
20.07.09: Review article about high-accuracy Penning trap mass measurements
Klaus Blaum et al. provide an overview of high-accuracy Penning trap mass measurements with stored and cooled exotic ions in a just published Journal of Physics B review article. High-accuracy mass values contribute significantly to various fields of physics. They provide access to nuclear and atomic binding energies, serve for comparison with nuclear models as well as for test of fundamental interactions such as quantum electrodynamics or weak interaction. In this review article the destructive time-of-flight ion-cyclotron-resonance technique (ToFICR) is briefly reviewed particularly in view of precision experiments on unstable nuclei. Further the basic features of international experimental facilities for mass determinations of radionuclides are described. Selected important applications of high precision mass measurements are given and future developments as well as planned facilities are discussed. Read more in the review article ... >

Link to the entire Special issue on modern applications of trapped ions external Link
10.06.09: Rotational Cooling of HD+ Molecular Ions by Superelastic Collisions with Electrons
A just published Physical Review Letters article reports the results of rotational cooling of HD+ molecular ions by superelastic collisions (SEC) with electrons. Strong rotational cooling could be observed when an HD+ beam was merged with cold electrons in a heavy ion storage ring. The electron beam with an internal temperature of 33 K reduced the rotational temperature of the ions from about 1500 K to 125 K within only 8 s and stabilized it at this low value in the simultaneously acting thermal radiation field at an ambient temperature of 300 K. The cooling due to superelastic collisions is well described by recently calculated theoretical rate coefficients, which predict the ΔJ = -2 SEC rate coefficients to be dominant. These rate coefficients are of the order of (1-2) x 10-6 cm3 s-1 and are thus of the same size as the vibrational (Δν = -1) SEC rates measured for H2+. Read more in the article ... >
20.03.09: First discovery of 229Rn by Penning-trap mass measurement
D. Neidherr et al. report in a just published Physical Review Letters article about the first direct mass measurements on the seven neutron-rich radon isotopes 223-229Rn by precision mass spectrometry. The measurements were performed at the double Penning-trap mass spectrometer ISOLTRAP located at the on-line isotope separator facility ISOLDE at CERN, Geneva. The experiment especially marks the first discovery of a new nuclide, 229Rn, by Penning trap mass measurement. The new high-accuracy mass data provide significant extensions of known masses, which are important for understanding the binding of the heavy nuclei, which have an impact on nucleosynthesis in the actinide region, and which provide new constraints on modern models of structure and of the mass surface. Read more in the article ... >
26.02.09: Enhanced Sensitivity of Nuclear Binding Energies to Collective Structure
A recent Physical Review Letters article reports the results of new studies of calculated collective contributions to nuclear binding and separation energies.
As hitherto well-known in nuclear physics nuclear masses and binding energies reflect the sum of all nucleonic interactions, which lead to nuclear structure in all its various forms. The article points out, that the interrelation between nuclear masses and nuclear structure is much more sensitive than previously expected. Especially deformed nuclei near neutron mid-shell (N=104) show this high sensitivity. The letter focuses on the binding and separation energies calculated with the IBA model and illustrates the results using the example of the N=100 Er isotope.
Because of the unexpected high sensitivity measured separation energies may even help understand the structure and intrinsic excitations in well-deformed nuclei and yield new strategies for modelling such nuclei. Furthermore the new findings will have important implications for future high-precision mass measurements with advanced Penning traps and storage ring techniques. Read more in the article ... >
13.02.09: Nuclear Charge Radii of 7,9,10Be and the One-Neutron Halo Nucleus 11Be
In a just published Physical Review Letters article W. Nörtershäuser et al. describe the nuclear charge radii measurements of 7,9,10,11Be by on-line frequency-comb based collinear laser spectroscopy at ISOLDE/CERN, Geneva.
The measurements are based on very accurate atomic structure calculations which are currently only possible for atoms with at most three electrons. Thus the spectroscopy was performed on Be+ ions. Most important goal was the charge radius determination of the one-neutron halo nucleus 11Be. In halo nuclei, individual nucleons can reside far away from the nuclear core.
The charge radius decreases from 7Be to 10Be and then increases for the halo nucleus 11Be. The charge radius of 11Be was determined to be 2.463(16) fm. From a simple frozen-core two-body model a rms distance of about 7 fm between the halo neutron and the center of mass in 11Be was obtained in good agreement with elaborate nuclear-structure calculations. Read more in the article ... >
05.01.09: Mass Measurements beyond the Major r-Process Waiting Point 80Zn
In a very recently in Physical Review Letters published article S. Baruah et al. report results of high-precision mass measurements on neutron-rich zinc isotopes 71m,72–81Zn. The masses have been determined with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE, CERN.
Reliable nuclear data on the extremely neutron-rich nuclei participating in the rapid neutron-capture process (r process) are needed to compare the signatures of specific models with astronomical data.
In this experiments the mass of 81Zn has been determined for the first time and a relative mass uncertainty below 7 · 10-8 has been achieved. With the performed mass measurements, 80Zn is the first major waiting point along the path of the astrophysical r process where the mass differences with respect to its neighbor nuclides (79Zn and 81Zn) and thus the neutron-separation energy and neutron-capture Q-value are determined experimentally.
With the new data the astrophysical conditions required for the major waiting point 80Zn and its associated abundance signatures to occur in r-process models can now be mapped precisely. Read more ... >
02.01.09: High-precision mass and charge radius measurements on 17–22Ne and the proton-halo candidate 17Ne
A recent Physical Review Letters article reports high-precision mass and charge radius measurements on 17–22Ne. The measurements were performed at ISOLDE/CERN and especially include the Two-Proton-Halo Candidate 17Ne. For the mass measurements the neon ions were investigated with the ISOLTRAP setup using the precision Penning trap applying a time-of-flight cyclotron resonance technique. In this experiments the 17Ne mass uncertainty has been improved by factor 50. The neon charge radii were investigated by collinear laser spectroscopy with sensitive detection by ion counting. The charge radii of 17–19Ne have been determined for the first time.
Glauber theory, Shell-model descriptions and three-body calculations don't lead to a consensus on a two-proton-halo formation in 17Ne. It can be seen as an 15O core in its ground state with an admixture of two protons in d2 or halolike s2 configurations. Since 17Ne depends sensitively on the halo protons, its charge radius provides a test of model predictions.
The fermionic molecular dynamics model (FMD model) explains remarkably well the large structural differences between the neon isotopes. It attributes the large charge radius of 17Ne to an extended proton configuration with an s2 component of about 40%. In 18Ne the smaller charge radius is due to a significantly smaller s2 component. The charge radii increase again for 19–22Ne due to cluster admixtures. Read more ... >