Showing papers by "Lutz Schweikhard published in 2000"
TL;DR: 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 1 keV/amu, e.g., in solar wind collisions.
Abstract: K-shell x-ray emission following low-energy charge exchange collisions (
84 citations
TL;DR: In this paper, the structural and energetic properties of the adducts formed by adsorbing methanol onto size-selected gold clusters are investigated by infrared photodissociation of trapped Aun+(CH3OH)m, n=1−10,15 and m=1-3.
Abstract: Structural and energetic properties of the adducts formed by adsorbing methanol onto size-selected gold clusters are investigated by infrared photodissociation of trapped Aun+(CH3OH)m, n=1–10,15 and m=1–3. The excitation of vibrational modes of methanol leads to the desorption of neutral molecules which is monitored by time-of-flight mass spectrometry. Spectra are obtained by measuring the fragment ion intensity as a function of photon energy. The C–O stretching vibration of adsorbed methanol changes discontinuously with cluster size. By comparison with Car–Parrinello calculations this change is traced back to the dimensionality of the gold clusters. The number of photons necessary for the desorption of methanol molecules provides an estimate of the respective separation energies.
61 citations
TL;DR: In this article, the abundance spectra of doubly and triply charged Au n + in the size range n =12 to 72 have been captured and stored in a Penning trap, size selected and subjected to an electron beam.
39 citations
TL;DR: In this article, the first observation of photodetachment of electrons from metal cluster dianions was made, and both doubly and triply charged titanium clusters were observed.
Abstract: 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, Ti552- clusters are selected and excited by a laser pulse, which leads to the emission of an excess electron: Ti552-→ e− + Ti55-.
17 citations
TL;DR: In this article, it is demonstrated how by selection of pre-precursor cluster ions and collision-induced dissociation an ensemble of Ag 2 n 2+ can be produced, which is not contaminated by Ag n + clusters of the same size-to-charge state ratio, n / z.
12 citations
16 Nov 2000
TL;DR: In this article, the authors used x-ray spectroscopic techniques to study charge transfer reactions involving highly charged ions up to U91+ in plasmas, where electron capture is enabled by electron capture into states with low orbital angular angular momentum, mainly l=1.
Abstract: Charge transfer reactions involving highly charged ions up to U91+ are being studied using x-ray spectroscopic techniques. The measurements are performed using ions produced in situ in a cylindrical trap with very low kinetic energy (⩽3 eV/amu). The observed K-shell and L-shell x-ray emission show prominent features from high-n levels decaying to the ground level. Such emission can serve as a diagnostic marker for charge transfer processes in plasmas, for example in cometary comae or in ion traps. The emission is enabled by electron capture into states with low orbital angular momentum, mainly l=1. The observed spectra, thus, provide a handle on determining the fraction of electron capture into low-l states that can be used for testing theoretical models in the limit of low collision energy. The present paper summarizes the progress made to date.
7 citations