Gas‐Phase Reactivity of Sulphur Cluster Cations and Anions by FT‐ICR Investigations

Abstract

The gas phase reactions of sulphur cluster cations S italicn+ (n = 2,…,8) and anions S italicn− (n = 2,…,6), have been studied by means of a Fourier‐Transform‐Ion‐Cyclotron‐Resonance (FT‐ICR) mass spectrometer. While with several simple gases no reactions, besides some fragmentation, were observed, some of the clusters were found to be reactive towards NO, NH3 and particularly NO2. Where product ions were detected, relative and absolute rate constants were extracted from the data, while only upper limits could be estimated for those systems which do not yield observable amounts of products. We discuss in most detail the reactions of NO2 which reacts with both the anions and cations. By comparing the reactivities of clusters of differing charge we try to deduce the influence of charge versus structure.

Collisional Activation of N2O Decomposition and CO Oxidation Reactions on Isolated Rhodium Clusters

“…29,30 Rhodium-containing clusters are generated by laser ablation of a rotating rhodium foil in the presence of a pulsed carrier gas. pressures quoted below have been corrected for the instrumental geometry factor which accounts for the relative positions of the ICR cell and the pressure gauge, 31 and for the sensitivity of the pressure gauge towards the gases used. 32 Two conceptually different collision experiments have been performed: Neglecting any (small) initial cyclotron motion, ions thus excited achieve lab frame cyclotron orbit speed, v exc , of: [33][34][35][36][37][38] (1)…”

Carbon-carbon bond formation in the reaction of hydrated carbon dioxide radical anions with 3-butyn-1-ol

“…The reaction is monitored by recording a series of mass spectra with increasing reaction delays. Pressure was calibrated following standard procedures [72][73][74].…”

Ion–molecule reactions of CoAr6+ with nitrogen oxides N2O, NO, and NO2: measuring absolute pressure by shock-freezing of the collision complex

“…The clusters are most likely much colder than this value, since no dissociation is observed. A widely used pressure calibration method for FT-ICR-MS takes an empirical geometric factor G and the chemical sensitivity x R of the gauge into account [21,22]. The chemical sensitivity x R depends on the polarizability α of the reactant molecules following the empirical relationship introduced by Bartmess and Georgiadis [2]:…”

“…In the region of 10 -10 -10 -7 mbar, measuring absolute pressure is not a trivial task. Different ionization probabilities have an effect on the reading, but it also depends on the gauge voltage, geometry and several other instrumental effects [3,13,21,22]. Standard ionization gauges are calibrated against nitrogen [1,4,23].…”

“…The gauge sensitivity, however, is not the only effect that makes the determination of absolute pressures inside the ICR cell difficult. Equally important is the geometry of the vacuum chamber, in particular the relative position of the ICR cell, the ion gauge and the turbomolecular pump, which can be accounted for with an instrument-specific geometry factor [13,22]. The geometry factor does not account for the different pumping efficiency of gases with high sticking coefficients.…”