Formation of doubly charged negative ions in the gas phase by collisionally-induced “ion pair” formation from singly charged negative ions

A versatile setup for studying size and charge-state selected polyanionic nanoparticles

Using the example of metal clusters, an experimental setup and procedure is presented, which allows for the generation of size and charge-state selected polyanions from monoanions in a molecular beam. As a characteristic feature of this modular setup, the further charging process via sequential electron attachment within a three-state digital trap takes place after mass-selection. In contrast to other approaches, the rf-based concept permits access to heavy particles. The procedure is highly flexible with respect to the preparation process and potentially suitable for a wide variety of anionic species. By adjusting the storage conditions, i.e., the radio frequency, to the change in the mass-to-charge ratio, we succeeded in producing clusters in highly negative charge states, i.e., Ag₈₀₀ ^7-. The capabilities of the setup are demonstrated by experiments extracting electronic and optical properties of polyanionic metal clusters by analyzing the corresponding photoelectron spectra.

High production of small organic dicarboxylate dianions by DESI and ESI

A significant production of gas-phase dicarboxylate dianions has been observed in standard ESI and DESI during the analysis of small organic dicarboxylic acids under moderate or highly alkaline conditions. In ESI, this can be attributed to an excess of hydroxyl ions (OH(-)) which favor the formation of an high amount of dianions in solution, contemporarily trapping the potential counter ions during the ESI process. The results obtained in DESI highlight the role of the surface in trapping the counter-ions during desorption process and determining the ultimate nature of the observed gas-phase ions.

Four decades of joy in mass spectrometry

Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career.

Formation and characterization of the sulfur-containing distonic radical anion, [Formula: see text], in the gas phase, in the gas phase

The reactions of the atomic oxygen radical anion O(-) with CH3-S-CH2-CN m the gas phase have been examined with Fourier transform ion cyclotron resonance in combination with tandem mass spectrometric experiments performed with a double-focusing quadrupole hybrid instrument. Deuterium labeling has revealed that the O(-) ion reacts with CH3-S-CH2-CN by proton abstraction from the methylene group as well as by competing 1,1- and 1,3-H 2 (+) abstractions to afford isomeric radical anions. High kinetic energy (8 keV) collision-induced charge reversal experiments indicate that the 1,1-H 2 (+.) -abstraction leads to a [Formula: see text] carbene ion, whereas the 1,3-H 2 (+) abstraction yields a novel sulfur-containing distonic radical anion, which is formulated as [Formula: see text].

Mass spectrometry and its use in tandem with laser spectroscopy

Mass spectrometry is undergoing rapid development, especially with the extension of its range into the hundreds of kilodaltons, the emergence of the quadrupole ion trap as a high-performance instrument, and the development of techniques for recording three-dimensional spectra. These advances are summarized in this review; in addition, the power of the combination of lasers and mass spectrometers is given particular emphasis. Their combination has contributed recently to chemical dynamics, to the study of cluster structure and reactivity, and to the elucidation of the properties of highly excited molecules and ions.