Reactions of simple hydrocarbons with Nb+n: Chemisorption and physisorption on ionized niobium clusters

Abstract

In a Fourier transform-ion cyclotron resonance mass spectrometer the gas phase reactivities of niobium clusters Nb+n (n=1–28) with molecular hydrogen, water, methane, ethane, n-propane, n-heptane, cyclohexane, acetylene, ethylene, allene, benzene, propene, toluene, xylene, and acetonitrile were investigated under single collision conditions as well as the reactivities of oxidized niobium cluster cations with ethylene and benzene. The reactions of larger clusters with a variety of unsaturated hydrocarbons are believed to proceed via long lived ‘‘physisorbed’’ addition intermediate complexes, which subsequently rearrange to form ‘‘chemisorbed,’’ extensively dehydrogenated final products. The overall reaction seems to proceed with near collision rates, almost independent of cluster size. In some cases also the physisorbed primary products are stabilized and detected. Their yields depend sensitively on the specific nature of the reactant, and on the niobium cluster size n. Fully saturated hydrocarbons unable to form the long lived complexes are unreactive with respect to the larger (n≳7) Nb+n clusters. Smaller clusters with n≤7 seem to react by a different, prompt reaction mechanism. The rate of this reaction steeply decreases, and the degree of product dehydrogenation increases with n.

Infrared spectroscopy of O˙− and OH− in water clusters: evidence for fast interconversion between O˙− and OH˙OH−

“…The reactant ions, (H 2 O) n À , were generated in a home-built external source 28 by laser vaporization of a solid zinc target and supersonic expansion of the hot plasma in a helium/water gas pulse. 30,31 The anionic water clusters were carried from the ion source into the 34 At each studied wavelength, a mass spectrum was taken after irradiating all clusters simultaneously, followed by recording a mass spectrum without laser irradiation.…”

“…The IRMPD experiments were performed using a 4.7 T Fouriertransform ion cyclotron resonance (FT-ICR) mass spectrometer 28,29 equipped with a tunable optical parametric oscillator (OPO). The reactant ions, (H 2 O) n À , were generated in a home-built external source 28 by laser vaporization of a solid zinc target and supersonic expansion of the hot plasma in a helium/water gas pulse.…”

Photodissociation and photochemistry of V+(H2O)n, n = 1–4, in the 360–680 nm region

“…The experiments are performed on a modified Bruker/Spectrospin CMS47X FT-ICR mass spectrometer, described in detail before [38][39][40]. Hydrated vanadium ions are produced by laser vaporization [41][42][43] of a solid vanadium disc, followed by supersonic expansion of the hot plasma in helium seeded with water vapor [29,39].…”

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

“…The experiments were performed on a modified Bruker Spectrospin CMS47X mass spectrometer [36][37][38]. In the new setup in Kiel it is equipped with a 4.7 T unshielded superconducting magnet, an APEX III data station, a Bruker infinity cell, TOPPS ion optics power supply, and an ICC2 Infinity Cell Controller with BCH preamplifier.…”