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The performance of a multi-reflection time-of-flight (MR-ToF) mass spectrometer is evaluated under the use of four voltage feedback loops to actively regulate its mirror potentials. Different electronic hardware is characterized to find the most useful configuration for parallel regulation of all of the MR-ToF analyzer's reflecting potentials. The gain in mass resolving power for low-abundance ion species is demonstrated by measuring pairs of molecular isobars of zinc clusters and analyzed in the context of expected flight-time fluctuations. For higher-abundance species, the resolving powers reached in short- and long-term measurements are probed with bismuth-cluster ions, resulting in values up to 500 000 and 200 000, respectively, in the absence of offline corrections. Additionally, feedback-loop regulation is found to be advantageous for changes of experiment cycles in which voltages are switched for, e.g., ion ejection. [ABSTRACT FROM AUTHOR]

Repeated switching of electric potentials within a single experimental cycle is introduced for a multi-reflection time-of-flight mass spectrometer (also known as an electrostatic ion beam trap) in order to eject different ion species after different storage times. The method is demonstrated with two cluster ions with considerably different mass-to-charge ratios (the A = 624 and 832 isotopologues of P b 3 + and P b 4 + , respectively) for the specific case where the sequential ejections result in an identical number of revolution periods. Thus, the ions' flight lengths are identical, and the resulting time-of-flight values allow single-reference mass determination. The requirements for the switching time window are studied in detail. For the present system and ion pair, the relative mass uncertainty is found to be 3 · 10−7 for short measurements (≈10 min) and 6 · 10−8 for longer ones (≈2 h). [ABSTRACT FROM AUTHOR]

The Greifswald multi-reflection time-of-flight setup has been extended with a magnetron sputtering gas aggregation source for the production of atomic cluster ions with sizes ranging from a single to thousands of atoms. This source, combined with a newly added quadrupole mass filter and a linear Paul trap, opens up the possibility of many new atomic-cluster studies not feasible with the setup before. The new components and their interfacing with the previous setup are described, and benchmarking as well as the first experimental results are presented. The capability of the system to handle singly charged ions with masses of several ten thousand atomic mass units is demonstrated. [ABSTRACT FROM AUTHOR]

Cationic and anionic clusters of the group-14 elements carbon, silicon, germanium, tin, and lead are produced by high-vacuum laser ablation and studied with a multi-reflection time-of-flight mass spectrometer. In-trap photodissociation is performed for cluster species in the size range n = 2–10. The clusters’ production rates as well as their dissociation pathways are used to probe the nonmetal–metal transition throughout the group. Carbon clusters show neutral-trimer break-off, while those of the other elements evaporate neutral monomers and, in some cases, form specific charged fragment sizes. [ABSTRACT FROM AUTHOR]

Abstract: Time-resolved electron emission after photoexcitation in a Penning trap has been applied to size and charge-state selected dianionic gold clusters, . An exponential decrease of the relative abundance was recorded, along with a corresponding appearance of the monoanion . This constitutes the first observation of delayed electron emission from a metal-cluster dianion. By application of the Weisskopf decay-rate model to the emission rate the binding energy of the second surplus electron was found to be 0.91(5)eV. This value compares favourably with the second electron affinity as expected from the liquid drop model. [Copyright &y& Elsevier]

Abstract: The technique of time-resolved photodissociation in a Penning trap has been extended from cationic to anionic metal clusters. As a proof of principle the size-selected gold clusters Au14 − and Au17 − have been investigated. Superposed on the expected exponential decrease (increase) of the intensity of the precursor (product) cluster ion an oscillation of the yield is observed. This oscillation, which has not been noticed in the case of cations, is attributed to the magnetron motion of the ions in the trap. Reaction-rate constants for the monomer evaporation have been determined. The dissociation energies deduced from the Weisskopf rate equation are compared to extrapolations from model-free dissociation energies of positively charged gold clusters. [Copyright &y& Elsevier]

The influence of mass-over-charge ratio (m/z) changing reactions on the motion of stored ions in a Penning trap (ion cyclotron resonance cell) is investigated. For all three motional modes, the cyclotron, the magnetron and the axial (trapping) motion, the influence of the m/z change on the amplitude is discussed. In cases of spontaneous m/z increase, as for electron loss from a polyanionic particle, the extension of the radial ion motion is increased and thus the ions may be lost from the trap. As an example, measurements on the electron emission from doubly charged cluster anions are discussed. [Copyright &y& Elsevier]

Presents information on the Atomic High-Precision Mass Spectrometry symposium held by the German Physical Society. Topics related to atomic mass discussed at the symposium; Lecturers; Highlights of the symposium.

Die Massen von Radionukliden sind wichtig, um Kernmodelle zu testen oder astrophysikalische Fragestellungen, wie den Aufbau von Neutronensternen, zu beantworten. Aufgrund ihrer oft geringen Halbwertszeit lassen sie sich jedoch nur schwer messen. Kürzlich gelang es der ISOLTRAP-Gruppe am Forschungszentrum CERN, die Massen von 54Ca und 82Zn mit hoher Genauigkeit zu bestimmen. Damit erhält man Aufschluss über das Wirken von Dreikörperkräften innerhalb des Atomkerns sowie über die Elemententstehung in der Kruste von Neutronensternen. [ABSTRACT FROM AUTHOR]

Am GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt ist erstmals die direkte Messung der Stärke von Schaleneffekten in sehr schweren Atomkernen mit über 100 Protonen gelungen. Durch hochpräzise Massenmessungen an den Transuranen Nobelium und Lawrencium konnten diese Schaleneffekte für 152 Neutronen bestimmt werden. Die Ergebnisse liefern Informationen über die Kernstruktur superschwerer Elemente und dienen dazu, die Vorhersagen über Lage und Ausdehnung der 'Insel der Stabilität' zu verbessern. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Novel approaches for capture and in-trap selection of ions in an electrostatic ion beam trap/multi-reflection time-of-flight device. • Multiple capture pulses are used to inject ions while previously-stored ones are retained in the mirror potentials or the in-trap lift. • Technique of transversal ejection is used with multiple input deflector functions to selectively retain ion species of interest with different mass-to-charge ratios. Abstract The present study introduces new approaches for the capture/injection and selection of ions with large mass-to-charge (m / q) differences in an electrostatic ion beam trap (EIBT) or multi-reflection time-of-flight (MR-ToF) device. While no m / q -dependent storage criterion exists for devices of this nature, the process of injecting ions into the trap relies on a timed potential switching and is therefore mass-selective to some extent. To partially circumvent this restriction, the approach of sequential capture is presented, where additional ion species are captured while already-stored ones are unaffected by the switching pulses. Specifically, it is possible to perform a full in-trap lift capture pulse while a given, already-stored ion species is reflected in a mirror potential or passes through the lift electrode itself. Additionally, the technique of ion selection by means of transversal ejection from the trap is extended to allow ion species with large m / q differences to be retained. To this end, deflector functions with different frequencies are added with an AND logic and supplied to an in-trap deflector electrode. The combination of both techniques allows the simultaneous storage of size-selected ion species with an m / q ratio surpassing 4 : 1 at the present setup, where the single-pulse lift capture is restricted to a ratio of only 1.9. [ABSTRACT FROM AUTHOR]

Polyanionic lead clusters have been produced by electron attachment in a Penning trap. The smallest dianionic and trianionic lead clusters observed were of size n = 28 and n = 69, respectively and the appearance sizes following the definition of Martinez et al. (2015) are n = 39 and n = 80, respectively. In addition, and in contrast to previous measurements on clusters of several other metals, decay reactions are observed in the cluster size range of n = 14–49. The decay products are similar, but not identical, to those reported for the photodissociation of Pb n − . [ABSTRACT FROM AUTHOR]

Abstract: A new type of digital ion trap is introduced, namely a Paul trap with 3-state digital driving voltages. The stability diagram has been mapped, i.e. the relative storage efficiency with respect to the trapping parameters has been measured. The results show, that the performance of the 3-state digital ion trap can be described in terms of the conventional (2-state) digital ion trap, where the trapping parameters are defined, again, according the zeroth and first order Fourier component of the driving field. [Copyright &y& Elsevier]

Abstract: The Paul trap with a rectangular driving field, known as digital ion trap (DIT) has been investigated by mapping the stability diagram, i.e., measuring the relative storage efficiency with respect to the trapping parameters, and comparison to the conventional Paul trap with harmonic guiding field. The results show that the performance of the DIT can be described in terms of the conventional trap, when the trapping parameters are redefined according to the zeroth and first order Fourier component of the driving field. The higher harmonics seem to have only little influence. [Copyright &y& Elsevier]

Similar to fingerprints, atoms can be identified by their masses—when weighted with sufficient accuracy. The mass of an atom reflects all internal forces and thus carries information on the strong, weak, and electromagnetic interactions both of the nucleons and the electrons. Thus, atomic masses are addressed in numerous applications, at different levels of accuracies. For atomic- physics applications, like quantum electrodynamics (QED) tests or electron binding energies, relative mass uncertainties down to the current limit of about δm/m ≈10-11 can be essential. [ABSTRACT FROM AUTHOR]

A recently developed method to determine dissociation energies has been applied to positively charged silver clusters of size n=14, 15, 16 and 18. The method uses a combination of sequential and single step decays. It requires an uncalibrated thermometer which here is provided by the evaporation rate constants of the product clusters. For this purpose, earlier measurements [J. Chem. Phys. 57 (1998) 2786] are reanalyzed with the new method. The resulting dissociation energies are compared with the liquid drop values and the measured decay rate constants with expected rate constants from detailed balance theory. [Copyright &y& Elsevier]

A series of multi-reflection time-of-flight (MR-ToF) spectra is recorded with increasing ion flight times and added up to a single transient. It shows periodic ToF-signal trains for each ion species revolving between the MR-ToF analyzer's mirrors. This is used to perform a "comb-sampling" evaluation previously devised for analysis of capacitive-pickup signals (Greenwood et al., Rev. Sci. Instrum. 82 (2011), 043103). The recording and evaluation focuses on simultaneously measuring the full range of trapped ions for wide-band mass spectrometry. The comb-sampling technique is revisited for the present transients, as it is the first time it is used for comparatively background-free single-ion-counting data. [Display omitted] • Interweaved multi-reflection time-of-flight (MR-ToF) data acquisition for wide-band ion tracking. • MR-ToF transient shows trains of ToF signals for each captured ion species. • Wide-band high-resolution evaluation via comb sampling. [ABSTRACT FROM AUTHOR]

Negatively charged tin clusters offer a broad range of decay products, as observed after electron-cluster interactions [S. König, M. Wolfram, S. Bandelow, G. Marx, L. Schweikhard, Eur. Phys. J. D 72, 153 (2018)]. To get further insight into their decay pathways, size and charge-state selected clusters Snn- and Snn2- were photo-excited at the ClusterTrap setup by 532 nm Nd:YAG laser pulses. For small mono-anionic precursor clusters containing up to n ≃ 45 atoms, Snn-7- and Snn-10- are observed as preferred ionic fragments. For bigger clusters a transition to neutral monomer evaporation was found. In the case of di-anionic precursors, preferred decay products are Sn10- and Snn-10-, indicating fission similar to the case of the group 14 neighbor element lead [S. König, A. Jankowski, G. Marx, L. Schweikhard, M. Wolfram, Phys. Rev. Lett. 120, 163001 (2018)]. Furthermore, doubly charged fragment clusters such as Snn-72- are observed, originating from break-off of neutral heptamers Sn7, a behavior which has not been observed previously for di-anionic clusters. [ABSTRACT FROM AUTHOR]

A development in multi-reflection time-of-flight (MR-ToF) mass spectrometry is presented with which isobars are resolved by means of an offline correction with the signal of a non-isobaric ion species. The method is demonstrated for a pair of Cr 2 + isobars with a relative mass difference of 1.8 ∙ 10 - 5 , with either an additional, non-isobaric Cr 2 + or a CrO + ion appearing in the same time-of-flight spectrum, although at a different number of revolutions during the same storage time. This is in contrast to earlier applications where ToF shift corrections are performed with ions at identical revolution numbers, typically isobars that are also acting as mass-reference ions. It is shown that ions of virtually any mass simultaneously stored in the MR-ToF analyzer can be employed. This is particularly useful in situations where both the ions of interest and the reference ions for mass calibration have only small count rates not sufficient for the ToF-shift corrections. For the present system, the resolving power increases by more than a factor of two when the offline drift correction is applied. [ABSTRACT FROM AUTHOR]

The decay of ion-bunches stored in the self-bunching mode of an electrostatic ion beam trap (EIBT) has been investigated as a function of the number of injected ions with the Cryogenic Trap for Fast ion beams (CTF) located at the Max Planck Institute for Nuclear Physics in Heidelberg. By use of the pickup-electrode signal the dependence of the characteristic bunch-spreading time τ , i.e. the time in which the bunch width increases by one third, on the number of injected ions is determined. For F − ions with an initial bunch length of 2.7 μs the spreading times are observed to increase approximately linearly with the number of injected ions and to reach a constant value of ∼10 s for ion numbers larger than 4 × 10 5 . [ABSTRACT FROM AUTHOR]

Ion traps are versatile tools for the investigation of gas-phase cluster ions, allowing, e.g., cluster-size selection and extended reaction times. Taking advantage of their particular storage capability of simultaneous trapping of electrons and clusters, Penning traps have been applied for the production of clusters with high negative charge states. Recently, linear radio-frequency quadrupole traps have been demonstrated to be another candidate to produce polyanionic clusters. Operation with rectangular, rather than harmonic, radio-frequency voltages provides field-free time slots for unhindered electron passage through the trap. Several aspects of electron-attachment techniques by means of Penning and radio-frequency traps are addressed and recent experimental results are presented. [ABSTRACT FROM AUTHOR]

Highlights: [•] Polyanionic metal clusters are produced in ion traps by electron attachment. [•] The mass limit of the Penning trap restricts the achievable anionic charge states. [•] An upgrade to a cylindrical 12-T Penning trap increases the mass limit. [•] Gold cluster tetra-, penta- and hexaanions are observed for the first time. [•] Dianionic clusters produced in an RFQ trap are charged up further in a Penning trap. [Copyright &y& Elsevier]

The appearance sizes of polyanionic metal clusters are investigated with respect to their charge states. To this end, free gas-phase aluminium clusters with up to 10 excess electrons have been produced by use of the Penning-trap based electron-bath method. Cluster sizes, forming a meta-stable polyanionic cluster with lifetimes of 0.1 s, 1 s or 10 s, show a systematic dependence on the charge state, which is described by a model for electron-emission. The origin of the observed dependence is discussed. [Display omitted] • Production of polyanionic aluminium clusters with up to 10 excess electrons. • Mean lifetimes assigned to meta-stable clusters by field-emission model. • Lifetime-related appearance sizes show systematic dependencies on charge states. • Origin of dependencies discussed using electron tunneling calculations. [ABSTRACT FROM AUTHOR]

Ion trajectories have been simulated for an assembly of a linear quadrupole ion-filter and a linear Paul trap with additional pin electrodes for MS SPIDOC, a project in preparation for the study of biomolecules by single-particle imaging with X-ray pulses. The ion-optical components are based on digital RF guiding and trapping fields. In order to carefully handle biomolecules over a wide mass-over-charge range, the module presented consists of separate components for filtering and accumulation/trapping in order to select the ions of interest and to convert the beam from a continuous ion source to ion bunches, respectively, as required for the experiments downstream. The present analysis focuses on the transmission efficiency and mass resolving power of the filter, as well as the buffer-gas-pressure-dependent ion capture and thermalization in the trap for the example of a mass-to-charge ratio equivalent to hemoglobin 15+ ions. The resulting optimized ion bunch delivered by the assembly is characterized. [Display omitted] • Proof-of-principle simulations of an assembly of an ion filter and a Paul trap for the study of heavy biomolecules. • Investigations of the transmission efficiency and mass resolving power of a digital-operated linear quadrupole filter. • Optimizations of trapping, thermalization, and ejection characteristics from a digital operated trap. [ABSTRACT FROM AUTHOR]

Abstract: The attempts to produce higher and higher charge states of anionic metal clusters in Penning traps by attachment of simultaneously stored electrons run into a dilemma: On the one hand, the size of the clusters, which are initially only singly charged, has to be increased to accommodate additional electrons. On the other hand, in order to attach to already highly-charged particles, electrons have to overcome the respective Coulomb barriers. Thus, for the conventional electron-bath technique the electrons need to be created at correspondingly higher trapping potentials. This leads to a conflict as the “critical mass”, above which the ion orbits are no longer stable, is inversely proportional to the trapping potential. However, as the critical mass is actually an upper limit of the mass-over-charge ratio, the introduction of a stepwise charging-up by repeated electron bathing after increase of the trapping potential allows one to reach higher and higher charge states. [Copyright &y& Elsevier]

Abstract: Capture and ejection of ions in electrostatic ion-beam traps and multi-reflection time-of-flight (MR-ToF) devices can be accomplished by pulsing the potential of only a single drift tube inside of the device in contrast to the conventional switching of the ion-mirror voltages. In addition to its simplicity, the new method allows to set the position of the time-focus plane at a given ion detector or ion-beam separator without the need of any further hardware. The position can be adjusted easily by the choice of the pulse height of the potential switch. [Copyright &y& Elsevier]

Dipolar and single-phase two-electrode quadrupolar detection schemes have been investigated at a Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) setup built for the KATRIN experiment at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg. We present first experimental results of Li signals from a cylindrical Penning trap configuration for both detection schemes. While the prominent signal of the conventional dipolar detection scheme marks the reduced cyclotron frequency, the main signal for the quadrupolar detection appears at the sum of the reduced cyclotron frequency and the magnetron frequency. For ideal trapping fields, this sum frequency equals the ion cyclotron frequency ν = qB/(2 πm). Sidebands due to the combined motions of the cyclotron mode and magnetron mode are observed by quadrupolar detection which allows the determination of the respective combinations of eigenfrequencies. [ABSTRACT FROM AUTHOR]

A multi-reflection time-of-flight mass separator (MR-ToF-MS) for the enhancement of the performance of the Penning-trap mass spectrometer ISOLTRAP at the on-line isotope separator ISOLDE/CERN has been built and investigated at an off-line test facility. The MR-ToF-MS consists of two ion-optical mirrors between which oscillating ions are separated according to their different mass-over-charge ratios m/ q. Flight paths of several hundreds of meters are folded to an apparatus length of less than one meter. Preliminary tests resulted in a mass-resolving power of up to m/Δ m ≈ 80,000, and the separation was demonstrated for the isobaric ions CO and $\mathrm{N}_2^+$. The MR-ToF-MS will support the existing purification methods of ISOLTRAP and will extend the access to nuclides produced with high isobaric contamination yields at the ISOLDE facility. [ABSTRACT FROM AUTHOR]

Abstract: The application of an additional azimuthal quadrupolar electrostatic field to a Penning trap leads to a field configuration referred to as an elliptical Penning trap. The resulting changes of the radial ion motions have been investigated experimentally and by use of simulations. The eigenfrequencies, i.e., the magnetron frequency and the reduced cyclotron frequency , are found to be shifted with respect to those of the standard Penning trap , , respectively. As the shift of the magnetron frequency is larger than that of the reduced cyclotron frequency their sum is also a function of the ellipticity and no longer equal to the cyclotron frequency in the absence of an electric trapping field . The frequency shifts were investigated for argon and fullerene ions. The experimental studies were performed by time-of-flight (ToF) analysis of the ion cyclotron resonance and by Fourier-transform ion-cyclotron-resonance mass spectrometry (FT-ICR MS). The experimental and simulated values are in agreement with theoretical predictions [M. Kretzschmar, this issue] when the influence of higher multipole terms is taken into account. [Copyright &y& Elsevier]

Abstract: It is demonstrated how FT-ICR MS can be used to monitor both the coherent magnetron motion and the cyclotron motion of ions stored in a Penning trap. By use of the ICR signal intensity at the magnetron frequency, ν −, and the reduced cyclotron frequency, ν +, the manipulation of the ion motion by dipolar, quadrupolar, and octupolar excitation has been followed. In particular, the conversion between the magnetron and the cyclotron motion by quadrupolar and octupolar excitation at the corresponding resonance frequencies ν c = ν + + ν − and 2ν c, respectively, has been observed by detection of the magnetron and the cyclotron signal. While the ion motion under the influence of a quadrupolar excitation has already been studied extensively, the octupolar excitation has been introduced only recently. As compared to other techniques, such as the time-of-flight ion-cyclotron-resonance detection method, FT-ICR MS allows to simultaneously investigate the influence of an excitation on the cyclotron und the magnetron motional modes. [Copyright &y& Elsevier]

High-precision mass measurements as performed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN are an important contribution to the investigation of nuclear structure. Precise nuclear masses with less than 0.1 ppm relative mass uncertainty allow stringent tests of mass models and formulae that are used to predict mass values of nuclides far from the valley of stability. Furthermore, an investigation of nuclear structure effects like shell or sub-shell closures, deformations, and halos is possible. In addition to a sophisticated experimental setup for precise mass measurements, a radioactive ion-beam facility that delivers a large variety of short-lived nuclides with sufficient yield is required. An overview of the results from the mass spectrometer ISOLTRAP is given and its limits and possibilities are described. [ABSTRACT FROM AUTHOR]

Abstract: The reactions of stored ruthenium and osmium cations with oxygen have been studied in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. In case of osmium the reaction products OsO+ and have been observed and corresponding reaction-rate constants have been determined. In addition, there is an unreactive fraction of Os+ ions due to the presence of a slightly endothermic reacting ground state. Only the excited states react with oxygen. For ruthenium no spontaneous reaction with oxygen has been observed unless the cyclotron motion of Ru+ was excited. The results are discussed with respect to a similar investigation in a Penning trap-TOF mass spectrometer [U. Rieth, A. Herlert, J.V. Kratz, L. Schweikhard, M. Vogel, C. Walther, Radiochim. Acta 90 (2002) 337] and with respect to possible future studies of ion-molecule reactions of the homologous super-heavy element 108 (hassium). [Copyright &y& Elsevier]

A new Fourier transform ion cyclotron resonance mass spectrometer is described in three sections: magnet, vacuum system, and electronics/data system. Each component is described in detail (e.g., manufacturer's part numbers, drawings, circuit schematics, etc.). Of special interest is the high-frequency signal generation and processing required to extend the lower-mass limit for singly charged ions to 1 u. In particular, two new multiple heterodyne techniques for high-frequency measurements are described, as well as a method for producing a long-duration electron beam, and the implementation of z-axis ejection for selective removal of unwanted ions of various mass-to-charge ratios. [ABSTRACT FROM AUTHOR]

In the development towards the Multi Ion Reflection Apparatus for Collinear Laser Spectroscopy (MIRACLS), an optical detection region for the observation of fluorescent light is added to an electrostatic ion beam trap (EIBT). In addition to its use for highly sensitive collinear laser spectroscopy, this fluorescence detection is introduced as a diagnostics tool for the study of the ion dynamics inside an EIBT. First measurements of collision-induced fluorescence in an EIBT demonstrate the technique's diagnostics power by tracking the evolution of an ion bunch's temporal width over its storage time inside the ion trap. Thereby, the time-focus point of the ion bunch can be determined and the influence of space-charge effects in the EIBT can be investigated. Good qualitative agreement is obtained between the measured trend of temporal widths and the simulations of the ions' trajectories in the trap. Particularly, the observation of self-bunching on the ion-bunch structure for many simultaneously stored ions is reproduced. [ABSTRACT FROM AUTHOR]

Abstract: Size-selected monoanionic tin clusters Snn−, n = 7 − 75, are stored simultaneously with electrons in a Penning trap to produce poly-anionic clusters by electron attachment. In addition to doubly and triply charged clusters with the size of the precursors, fragments such as Sn−n−7, Sn−n−10 or Snn−15 are observed in the lower size range (n ≲ 50). The latter come along with the clusters Sn−10 and Sn−15, probably due to fission of doubly charged clusters as in the case of the group-14 neighbor-element lead [König et al., Phys. Rev. Lett. 120, 163001 (2018)]. Furthermore, prominent doubly charged products Sn2−n−15 seem to be produced by break-off of neutral decamers, a feature not yet observed for any other dianionic cluster. In addition, while almost no monomer evaporation is observed for singly charged clusters, this process does occur for doubly charged ones. Graphical abstract: [ABSTRACT FROM AUTHOR]

A method is presented to monitor the internal energy distribution of cluster anions via delayed electron detachment by pulsed photoexcitation and demonstrated on Co-4 in an electrostatic ion beam trap. In a cryogenic operation, we calibrate the detachment delay to internal energy. By laser frequency scans, at room temperature, we reconstruct the time-dependent internal energy distribution of the clusters. The mean energies of ensembles from a cold and a hot ion source both approach thermal equilibrium. Our data yield a radiative emission law and the absorptivity of the cluster for thermal radiation. [ABSTRACT FROM AUTHOR]

The recently introduced method of ion separation by transversal ejection of unwanted species in electrostatic ion-beam traps and multi-reflection time-of-flight devices has been further studied in detail. As this separation is performed during the ion storage itself, there is no need for additional external devices such as ion gates or traps for either pre- or postselection of the ions of interest. The ejection of unwanted contaminant ions is performed by appropriate pulses of the potentials of deflector electrodes. These segmented ring electrodes are located off-center in the trap, i.e., between one of the two ion mirrors and the central drift tube, which also serves as a potential lift for capturing incoming ions and axially ejecting ions of interest after their selection. The various parameters affecting the selection effectivity and resolving power are illustrated with tin-cluster measurements, where isotopologue ion species provide mass differences down to a single atomic mass unit at ion masses of several hundred. Symmetric deflection voltages of only 10 V were found sufficient for the transversal ejection of ion species with as few as three deflection pulses. The duty cycle, i.e., the pulse duration with respect to the period of ion revolution, has been varied, resulting in resolving powers of up to several tens of thousands for this selection technique. [ABSTRACT FROM AUTHOR]