Author
Lutz Schweikhard
Other affiliations: Michigan State University, Ohio State University, Heidelberg University ...read more
Bio: Lutz Schweikhard is an academic researcher from University of Greifswald. The author has contributed to research in topics: Penning trap & Mass spectrometry. The author has an hindex of 53, co-authored 337 publications receiving 9906 citations. Previous affiliations of Lutz Schweikhard include Michigan State University & Ohio State University.
Topics: Penning trap, Mass spectrometry, ISOLTRAP, Ion, Ion trap
Papers published on a yearly basis
Papers
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TL;DR: In this paper, a new cooling technique for heavy ions stored in a Penning trap was developed, where axial and cyclotron motions were cooled by buffer gas collisions, and the outward radial diffusion caused by the buffer gas was counteracted by an azimuthal quadrupole rf field.
496 citations
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TL;DR: The mass determination of the exotic calcium isotopes 53Ca and 54Ca is reported, using the multi-reflection time-of-flight mass spectrometer of ISOLTRAP at CERN, to establish a prominent shell closure at neutron number N = 32, in excellent agreement with the theoretical calculations.
Abstract: The properties of exotic nuclei on the verge of existence play a fundamental part in our understanding of nuclear interactions. Exceedingly neutron-rich nuclei become sensitive to new aspects of nuclear forces. Calcium, with its doubly magic isotopes (40)Ca and (48)Ca, is an ideal test for nuclear shell evolution, from the valley of stability to the limits of existence. With a closed proton shell, the calcium isotopes mark the frontier for calculations with three-nucleon forces from chiral effective field theory. Whereas predictions for the masses of (51)Ca and (52)Ca have been validated by direct measurements, it is an open question as to how nuclear masses evolve for heavier calcium isotopes. Here we report the mass determination of the exotic calcium isotopes (53)Ca and (54)Ca, using the multi-reflection time-of-flight mass spectrometer of ISOLTRAP at CERN. The measured masses unambiguously establish a prominent shell closure at neutron number N = 32, in excellent agreement with our theoretical calculations. These results increase our understanding of neutron-rich matter and pin down the subtle components of nuclear forces that are at the forefront of theoretical developments constrained by quantum chromodynamics.
369 citations
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TL;DR: The masses of six neutron-deficient rare holmium and thulium isotopes close to the proton drip line were determined with the SHIPTRAP Penning trap mass spectrometer with new proton separation energies derived from the measured mass values and compared to predictions from mass formulas.
Abstract: The masses of six neutron-deficient rare holmium and thulium isotopes close to the proton drip line were determined with the SHIPTRAP Penning trap mass spectrometer. For the first time the masses of the proton-unbound isotopes {sup 144,145}Ho and {sup 147,148}Tm were directly measured. The proton separation energies were derived from the measured mass values and compared to predictions from mass formulas. The new values of the proton separation energies are used to determine the location of the proton drip line for holmium and thulium more accurately.
273 citations
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11 Jan 1996-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The tandem Penning trap mass spectrometer ISOLTRAP has been set up at the on-line mass separator ISOLDE at CERN/Geneva for accurate mass measurements of short-lived nuclei with T 1 2 ≥ 1 s.
Abstract: The tandem Penning trap mass spectrometer ISOLTRAP has been set up at the on-line mass separator ISOLDE at CERN/Geneva for accurate mass measurements of short-lived nuclei with T 1 2 ≥ 1 s . The mass measurement is performed via the determination of the cyclotron frequency of an ion in a magnetic field. The design of the spectrometer matches the particular requirements for on-line mass measurements on short-lived isotopes. With the ISOLTRAP spectrometer masses of more than 70 radioactive nuclei have so far been determined with resolving powers exceeding one million and an accuracy of typically 10−7.
208 citations
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TL;DR: In this paper, a detailed study of the accuracy of the Penning trap mass spectrometer ISOLTRAP all expected sources of uncertainty were investigated with respect to their contributions to the uncertainty of the final result.
Abstract: For a detailed study of the accuracy of the Penning trap mass spectrometer ISOLTRAP all expected sources of uncertainty were investigated with respect to their contributions to the uncertainty of the final result. In the course of these investigations, cross-reference measurements with singly charged carbon clusters 12C+
n were carried out. The carbon cluster ions were produced by use of laser-induced desorption, fragmentation, and ionization of C60 fullerenes and injected into and stored in the Penning trap system. The comparison of the cyclotron frequencies of different carbon clusters has provided detailed insight into the residual systematic uncertainty of ISOLTRAP and yielded a value of 8×10-9. This also represents the current limit of mass accuracy of the apparatus. Since the unified atomic mass unit is defined as 1/12 of the mass of the 12C atom, it will be possible to carry out absolute mass measurements with ISOLTRAP in the future.
187 citations
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28,685 citations
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TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These
9,929 citations
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TL;DR: The crystallization and x-ray structure determination of a p-mercaptobenzoic acid–protected gold nanoparticle, which comprises 102 gold atoms and 44 p-MBAs, is reported, which is chiral, with the two enantiomers alternating in the crystal lattice.
Abstract: Structural information on nanometer-sized gold particles has been limited, due in part to the problem of preparing homogeneous material. Here we report the crystallization and x-ray structure determination of a p-mercaptobenzoic acid (p-MBA)-protected gold nanoparticle, which comprises 102 gold atoms and 44 p-MBAs. The central gold atoms are packed in a Marks decahedron, surrounded by additional layers of gold atoms in unanticipated geometries. The p-MBAs interact not only with the gold but also with one another, forming a rigid surface layer. The particles are chiral, with the two enantiomers alternating in the crystal lattice. The discrete nature of the particle may be explained by the closing of a 58-electron shell.
2,268 citations
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TL;DR: This review offers an introduction to the principles and generic applications of FT-ICR mass spectrometry, directed to readers with no prior experience with the technique, and lists accurate fundamental constants needed for ultrahigh-precision analysis.
Abstract: This review offers an introduction to the principles and generic applications of FT-ICR mass spectrometry, directed to readers with no prior experience with the technique. We are able to explain the fundamental FT-ICR phenomena from a simplified theoretical treatment of ion behavior in idealized magnetic and electric fields. The effects of trapping voltage, trap size and shape, and other nonidealities are manifested mainly as perturbations that preserve the idealized ion behavior modified by appropriate numerical correction factors. Topics include: effect of ion mass, charge, magnetic field, and trapping voltage on ion cyclotron frequency; excitation and detection of ICR signals; mass calibration; mass resolving power and mass accuracy; upper mass limit(s); dynamic range; detection limit, strategies for mass and energy selection for MSn; ion axialization, cooling, and remeasurement; and means for guiding externally formed ions into the ion trap. The relation of FT-ICR MS to other types of Fourier transform spectroscopy and to the Paul (quadrupole) ion trap is described. The article concludes with selected applications, an appendix listing accurate fundamental constants needed for ultrahigh-precision analysis, and an annotated list of selected reviews and primary source publications that describe in further detail various FT-ICR MS techniques and applications. © 1998 John Wiley & Sons, Inc., Mass Spec Rev 17, 1–35, 1998
1,964 citations