Showing papers by "Lutz Schweikhard published in 2002"
TL;DR: In this article, the cyclotron frequencies of singly charged carbon clusters C n + (n ≥ 2) were measured with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN.
Abstract: The cyclotron frequencies of singly charged carbon clusters C n + (n ≥ 2) were measured with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The present limit of mass accuracy δm/m 1.2.10−8 and the extent of the mass-dependent systematic shift (δm/m)sys 1.7(0.6).10−10/u (m − m ref) of the setup were investigated for the first time. In addition, absolute mass measurements by use of pure clusters of the most abundant carbon isotope 12C are now possible at ISOLTRAP.
59 citations
TL;DR: In this paper, the dianion yield is found to be a function of the potential well depth, presumably due to the repulsive Coulomb barrier for electron attachment in the case of metal cluster dianions.
34 citations
TL;DR: In this paper, time-resolved fragmentation measurements have been performed on stored, size-selected gold cluster ions that have been excited up to 15 eV by multiphoton absorption.
Abstract: Time-resolved fragmentation measurements have been performed on stored, size-selected gold cluster ions ${\mathrm{Au}}_{n}^{+}$ $(n=17--21)$ that have been excited up to 15 eV by multiphoton absorption. These excitation energies are far above the clusters' dissociation thresholds and initiate multistep sequential unimolecular dissociation by evaporation of neutral monomers. The measurements allow for the determination of a combination of kinetic-energy release and radiative cooling of the excited clusters. Also, previously determined model-independent values of the cluster dissociation energies are confirmed by the present measurements. The data are consistent with thermal values of the kinetic-energy release with no significant radiative cooling of the excited clusters.
15 citations
TL;DR: In this paper, a progress report on the investigation of metal clusters with an ion cyclotron resonance (Penning) trap is given on the recent studies on gold clusters, in particular the monomer and dimer evaporation is monitored as a function of cluster size.
15 citations
TL;DR: In this article, the first step to extend the until now direct mass measurements at ISOLTRAP to absolute mass measurements by using clusters of 12 C n + (n ⩾1) was taken.
11 citations
TL;DR: In this article, the dimer dissociation energies of gold cluster ions were determined with an extension of a recently developed model-independent method, which is needed in this method, and the measured values are D====== 2>>\s 2.50(9)(7) eV and D¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 2� 1.29(10)(6)-eV.
Abstract: The dimer dissociation energies of gold cluster ions Au
+
n
, n
= 9, 11, 13, 15 have been determined with an extension of a recently developed model-independent method. Monomer-dimer decay pathway branching ratios provide the energy dependent process which is needed in this method. The measured values are D
2
(
Au
+
9
) = 3.66(8)(9) eV, D
2
(
Au
+
11
) = 4.27(11)(8) eV, D
2
(
Au
+
13
) = 4.50(9)(7) eV and D
2
(
Au
+
15
) = 4.29(10)(6) eV.
11 citations
TL;DR: In this paper, size-selected anionic and dianionic gold clusters have been stored in a Penning trap and irradiated with the green light of a laser pointer, and two systems Au 7 − and Au 29 2− have been chosen.
8 citations
TL;DR: In this paper, the Mainz Cluster Trap is used as a model for SHIPTRAP, which is being installed behind the velocity filter SHIP (Separator for Heavy Ion reaction Products) at the Gesellschaft fur Schwerionenforschung at Darmstadt.
Abstract: Gas-phase ion chemistry in a Penning trap has been explored for future experiments on the chemical properties of the heaviest elements. The Mainz Cluster Trap, a Penning trap experiment devoted to metal cluster research, has served as a model apparatus for SHIPTRAP which is being installed behind the velocity filter SHIP (Separator for Heavy Ion reaction Products) at the Gesellschaft fur Schwerionenforschung (GSI) at Darmstadt. The reactions of stored Ru + and Os + with oxygen have been studied and the reaction products MO + and MO 2 + (M = Ru, Os) have been observed. The corresponding rate constants have been measured and the results are discussed with respect to future studies of similar ion-molecule reactions of the element 108 (hassium) in SHIPTRAP.
8 citations
TL;DR: In this paper, time-resolved photodissociation measurements of the sequential reaction Au8+CH3OH→Au8+→AU7+ and the direct reaction Au7+→AU7+ have been performed for several excitation energies.
Abstract: Time-resolved photodissociation measurements of the sequential reaction Au8+CH3OH→Au8+→Au7+ and the direct reaction Au8+→Au7+ have been performed for several excitation energies. The production rates and yields of the final state Au7+ in the sequential process are strongly influenced by the excitation energy deposited into the evaporated methanol molecule during the initial fragmentation step. Both the rate constants and yields can be fitted with a single parameter, the cluster–methanol binding energy.
8 citations
08 Mar 2002
TL;DR: In this article, the signals from each of two orthogonal pairs of opposed detection electrodes are acquired simultaneously and stored as real and imaginary parts of mathematically complex data using complex Fourier transformation.
Abstract: Positive and negative ions may be confined simultaneously in a nested open cylindrical Malmberg-Penning trap However, ion charge sign cannot be distinguished by conventional dipolar (linearly-polarized) detection with a single pair of opposed electrodes Here, the signals from each of two orthogonal pairs of opposed detection electrodes are acquired simultaneously and stored as real and imaginary parts of mathematically complex data Complex Fourier transformation yields separate spectra for positive and negative ions For a fullerene sample, experimental quadrature detection yields C60+ and C60− signals separated by ∼1440 u rather than by the mass of two electrons, ∼0001 u in conventional dipolar detection
8 citations
01 Feb 2002
TL;DR: Non-neutral plasmas are clouds of electrons or ions or anti-matter particles contained in a vacuum by magnetic and electric fields as discussed by the authors, and they give precise tests of basic theories of equilibrium, waves, and cross-field transport.
Abstract: Non-neutral plasmas are clouds of electrons or ions or anti-matter particles contained in a vacuum by magnetic and electric fields. Experiments on these simplest of plasmas give precise tests of basic theories of equilibrium, waves, and cross-field transport. Technical applications include positron beams, mass spectroscopy, quantum computing, and beams for free-electron lasers.
08 Mar 2002
TL;DR: The electron beam ion trap (EBIT) works as an ion trap even when the electron beam is switched off as discussed by the authors, which may sound like a contradiction in terms, but it is true that the EBIT can be used for ion confinement, charge exchange processes and ion mass measurements.
Abstract: Although it may sound like a contradiction in terms, the electron beam ion trap (EBIT) works as an ion trap even when the electron beam is switched off We present various experiments that exploit the “magnetic trapping mode” for investigations of ion confinement, charge exchange processes, atomic lifetime and ion mass measurements
08 Mar 2002
TL;DR: In this article, singly charged gold clusters from an external laser vaporization source have been transferred into a Penning trap and transformed into dianions by use of an electron bath of simultaneously stored electrons.
Abstract: Charge-changing reactions can lead to a significant change of the ion motion which may result in the loss of the ions from the trap. For the present experiments singly charged gold clusters from an external laser vaporization source have been transferred into a Penning trap and transformed into dianions by use of an electron bath of simultaneously stored electrons. The dianions have been investigated by collisional activation and laser excitation where electron emission has been observed as a cooling mechanism. Electron emission doubles the value of the cyclotron radius and in addition, the ions acquire a finite magnetron radius. This leads to an extension of the radial distance of the ion motion from the trap’s axis by a factor of about three.
CERN1
Book•
01 Jan 2002
TL;DR: Non-neutral plasmas are clouds of electrons or ions or anti-matter particles contained in a vacuum by magnetic and electric fields as discussed by the authors, which can be used to test basic theories of equilibrium, waves, and cross-field transport.
Abstract: Non-neutral plasmas are clouds of electrons or ions or anti-matter particles contained in a vacuum by magnetic and electric fields Experiments on these simplest of plasmas give precise tests of basic theories of equilibrium, waves, and cross-field transport Technical applications include positron beams, mass spectroscopy, quantum computing, and beams for free-electron lasers
TL;DR: The wichtigste Charakteristikum von zusammengesetzten Teilchen wie Molekulen, Fullerenen, Polymeren oor Clustern ist ihre Stabilitat as discussed by the authors.
Abstract: Das wohl wichtigste Charakteristikum von zusammengesetzten Teilchen wie Molekulen, Fullerenen, Polymeren oder Clustern ist ihre Stabilitat. Bisherige Methoden zur Bestimmung von Stabilitaten sind jedoch auf Modellannahmen angewiesen und daher mit Unsicherheiten behaftet. Ein neues Verfahren ermoglicht eine von Modellen unabhangige Bestimmung von Stabilitaten [1].