[en] 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

[en] The X-ray signature of charge exchange between highly charged L-shell iron ions and neutral gas atoms was studied in the laboratory in order to assess its diagnostic utility. Significant differences with spectra formed by electron-impact excitation were observed. In particular, a strong enhancement was found of the emission corresponding to n (le) 4 → n = 2 transitions relative to the n = 3 → n = 2 emission. This enhancement was detectable even with relatively low-resolution X-ray instrumentation (E/ΔE ∼ 10) and may enable future identification of charge exchange as a line-formation mechanism in astrophysical spectra.

[en] We describe and apply a new procedure that allows a direct determination of dissociation energies of polyatomic systems (clusters, fullerenes, polymers, and other molecules) without any modeling of the systems under investigation. As an example, we have determined the dissociation energies of a series of gold clusters Au⁺_n . A comparison with values obtained from statistical models of unimolecular dissociation shows that these models significantly fail to describe the data. In contrast, the new method yields values which are an order of magnitude more accurate, thus allowing one to experimentally set benchmarks for any theory which attempts to describe activated processes

No abstract available

[en] Titanium clusters are produced by laser vaporization of a metal wire in a helium gas pulse, stored in a Penning trap, size selected and transformed into multiply charged anions by electron attachment. Both doubly and triply charged titanium clusters are observed. For the first observation of photodetachment of electrons from metal cluster dianions, Ti₅₅^2- clusters are selected and excited by a laser pulse, which leads to the emission of an excess electron: Ti₅₅^2-→ e^- + Ti₅₅^-

[en] 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

[en] Collision induced dissociation is applied to study the fragmentation channels of multiply charged gold clusters, Au N2⁺, size N= 7 -35, and Au>_N3+}, N = 19-35, stored in an ion cyclotron resonance (Penning) trap. The main dissociation pathways are neutral monomer evaporation, Au>_NZ+to Au>_N-1Z+} + Au, for the larger and fission into a charged trimer plus the remaining cluster, Au>_NZ+to{}Au>_N-3(Z-1)+} +{}Au>₃₊}, for the smaller clusters. In the intermediate cluster size region an odd-even alternation of the two competing decay pathways is observed. In addition, for some specific cluster sizes there are indications of neutral dimer evaporation, Au>_NZ+to{}Au>_N-2Z++Au>₂}, and of extremely asymmetric fission of the form Au>_NZ+to Au>_N-1(Z-1)+} + Au⁺

[en] Size-selected metal-cluster dianions of the elements gold, silver and copper have been photoexcited by nanosecond-pulse and continuous laser irradiation, which leads to electron emission and monomer evaporation. In addition to the observation of these competing decay pathways, there is a reduction of the total cluster-ion intensity, which indicates the neutralization of dianions, i.e. the loss of both surplus electrons. In contrast, the activation of singly charged anionic clusters of the same type results primarily in dissociation by monomer evaporation and not by electron emission. These decay processes as observed for doubly and singly charged cluster anions suggest that the dianions emit two electrons simultaneously, i.e. in a correlated fashion. A classical conducting-sphere approximation confirms that the Coulomb barrier for symmetric two-electron emission is lower than the Coulomb barrier for the emission of a single electron. (paper)

No abstract available

[en] K -shell x-ray emission following low-energy charge exchange collisions (≤11 eV/amu ) has been measured for ten bare and hydrogenic ions up to U⁹¹⁺ . The data resolve capture into angular momentum states with ell=1 and provide a stringent test of theory. The assumption of Stark mixing of angular momentum states is inappropriate at such energies. Results from detailed calculations give a better description of the data, but significant discrepancies are noted. The measurements show that the hardness ratio of charge-exchange induced K -shell x-ray emission represents a diagnostic of the dynamics of ion-atom interactions in situations where the energy is below 1keV/amu, e.g., in solar wind collisions