Showing papers by "Lutz Schweikhard published in 2003"
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
TL;DR: In this paper, the performance of the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN has been considerably enhanced by the implementation of a magnetron phase locking mechanism.
Abstract: During the last two years, the performance of the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN (Geneva) has been considerably enhanced. Many technical improvements have been completed (i) to access nuclides that are produced in minute quantities of only 100 ions s−1, (ii) to increase the relative mass accuracy to ≤ 1 × 10−8 and (iii) to make accessible nuclei with a half-life of down to ≈ 5 ms. The major steps are presented, in particular the recent implementation of a magnetron phase locking mechanism which results in a significant reduction of the duration of ISOLTRAP's cyclotron measurements.
66 citations
TL;DR: In this article, metal clusters from a laser vaporization source are transferred to a Penning trap and subjected to a bath of simultaneously stored electrons, and after some reaction period multiply charged anionic gold, silver and copper clusters are observed if the clusters under investigation are large enough.
41 citations
TL;DR: It is found that the behavior of the branching ratio between monomer and dimer evaporation as a function of excitation energy depends on the metal under investigation, in particular, the slope of the energy dependence is positive for silver but negative for gold and copper cluster ions.
30 citations
TL;DR: In this article, a new experimental scheme has been developed which allows precision measurements of the dissociation energies of polyatomic species, which has been triggered by investigations on the delayed photodissociation of stored metal clusters.
Abstract: Ion traps are “wall-less containers” which allow the extended storage of selected species. During the storage various interaction steps may be repeatedly applied. To this end no further hardware has to be added - in contrast to beam experiments. In this progress report two examples of recent developments are presented: the experiments have been performed with metal clusters stored in a Penning (ion cyclotron resonance) trap. A new experimental scheme has been developed which allows precision measurements of the dissociation energies of polyatomic species. It has been triggered by investigations on the delayed photodissociation of stored metal clusters. However, the technique is also readily available for application to a broad variety of different species and it is not even restricted to trapping experiments. The second development is more closely connected with ion storage in Penning traps: by application of an “electron bath” singly charged anionic clusters can be converted into multiply charged species. Subsequently, they are charge selected and investigated with respect to their reaction upon excitation. In particular, preliminary results indicate that dianionic metal clusters emit two electrons upon photoexcitation whereas the singly charged species show dissociation.
29 citations
TL;DR: Atomic ion results from the Penning trap mass spectrometer ISOLTRAP, in which a carbon cluster ion source has recently been installed, are presented as an application in the field of precisionmass spectrometry.
Abstract: For accurate mass measurements and identification of atomic and molecular species precise mass calibration is mandatory. Recent studies with laser desorption/ionization and time-of-flight analysis of cluster ion production by use of fullerene and gold targets demonstrate the generation of atomic clusters for calibration purposes. Atomic ion results from the Penning trap mass spectrometer ISOLTRAP, in which a carbon cluster ion source has recently been installed, are presented as an application in the field of precision mass spectrometry.
21 citations
01 May 2003-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: The Penning trap mass spectrometer ISOLTRAP plays a leading role in mass-spectrometry of short-lived nuclides as discussed by the authors, and the recent installation of a radio-frequency quadrupole trap and a carbon cluster ion source allowed for the first time mass measurements on exotic nuclei with a relative uncertainty of δ m / m ≈ 1×10 −8.
Abstract: The Penning trap mass spectrometer ISOLTRAP plays a leading role in mass spectrometry of short-lived nuclides. The recent installation of a radio-frequency quadrupole trap and a carbon cluster ion source allowed for the first time mass measurements on exotic nuclei with a relative uncertainty of δ m / m ≈1×10 −8 . The status of ISOLTRAP mass spectrometry and recent highlights are presented.
21 citations
Abstract: A number of methods are available for the purpose of extracting dissociation energies of polyatomic particles. Many of these techniques relate the rate of disintegration at a known excitation energy to the value of the dissociation energy. However, such a determination is susceptible to systematic uncertainties, mainly due to the unknown thermal properties of the particles and the potential existence of 'dark' channels, such as radiative cooling. These problems can be avoided with a recently developed procedure, which applies energy-dependent reactions of the decay products as an uncalibrated thermometer. Thus, it allows a direct measurement of dissociation energies, without any assumption on properties of the system or on details of the disintegration process. The experiments have been performed in a Penning trap, where both rate constants and branching ratios have been measured. The dissociation energies determined with different versions of the method yield identical values, within a small uncertainty.
13 citations
26 Nov 2003
TL;DR: In this article, the time dependence of the attachment process and the influence of the trapping potential are reviewed, and the experimental results may be useful in the characterization of the stored electron ensemble.
Abstract: The simultaneous storage of electrons and anionic clusters in a Penning trap influences the trapping conditions of the ions, e. g. it results in a shift of the motional frequencies. In addition, the overlap of the electron cloud with the stored anions leads to electron attachment to the already charged anionic clusters. The time dependence of the attachment process and the influence of the trapping potential are reviewed. These experimental results may be useful in the characterization of the stored electron ensemble.
12 citations
TL;DR: In this article, the authors performed laser desorption/ionization cluster studies with a MALDI-TOF mass spectrometer on gold and fullerene targets to produce atomic clusters.
Abstract: Precise mass calibration is mandatory in many fields of mass spectrometry. We have performed laser desorption/ionization cluster studies with a MALDI-TOF mass spectrometer on gold and fullerene targets to produce atomic clusters. These investigations demonstrate that clusters are ideally suited for this purpose. Pulsed N 2 -laser and Nd:YAG-laser ablation was used to produce positively as well as negatively charged clusters. Earlier observations of dianionic metal clusters are confirmed. First results from the tandem Penning trap mass spectrometer ISOLTRAP using carbon clusters as mass references show how carbon clusters can be applied to precision mass spectrometry by providing absolute mass standards.
10 citations
TL;DR: In this paper, a new method to measure dissociation energies is reviewed and preliminary results on the competition between electron emission and neutral monomer evaporation from dianionic metal clusters are presented.
Abstract: The combination of ion storage in a Penning trap and photoexcitation by pulsed lasers has proven to be a versatile instrument in metal cluster research. Recent experiments which make use of both components allow a detailed study of the clusters' properties. In particular, a new method to measure dissociation energies is reviewed and preliminary results on the competition between electron emission and neutral monomer evaporation from dianionic metal clusters are presented.
TL;DR: In this article, a combination of sequential and single step decays was used to determine dissociation energies for positively charged silver clusters of size n = 14, 15, 16 and 18.
TL;DR: In this article, the mass uncertainty of singly charged carbon clusters 12C N + was measured with the ISOLTRAP apparatus. But the measurement of carbon clusters of different sizes has provided detailed insight into the final mass uncertainty.
Abstract: Cyclotron frequency measurements of singly charged carbon clusters 12C N + were carried out with the ISOLTRAP apparatus. The carbon cluster ions were produced externally by use of laserinduced desorption, fragmentation, and ionization of C60 fullerenes. They were injected into and stored in the Penning trap system. The observation of carbon clusters of different sizes has provided detailed insight into the final mass uncertainty achievable with ISOLTRAP and yielded a value of u(m)/m = 8 · 10-9. Since the unified atomic mass unit is defined as 1/12 the mass of the 12C atom, ISOLTRAP can now be used to carry out absolute mass measurements.