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Fourier transform ion cyclotron resonance mass spectrometry has been employed to study the reactions of gas-phase cationic cobalt clusters, Con+ (n=4–30), with nitric oxide, NO, and nitrous oxide, N2O, under single collision conditions. Isolation of the initial cluster permits detailed investigation of fragmentation channels which characterize the reactions of all but the largest clusters studied. In reaction with N2O, most clusters generate the monoxides ConO+ without fragmentation, cobalt atom loss accompanying only subsequent reactions. By contrast, chemisorption of even a single NO molecule is accompanied by fragmentation of the cluster. The measured rate coefficients for the Con++N2O reaction as a function of cluster size are significantly smaller than those calculated using the surface charge capture model, while for NO the rates are comparable. The reactions have been studied under high coverage conditions by storing clusters for extended periods to permit multiple reactions to occur. This leads to interesting chemistry on the surface of the cluster resulting in the formation of stable oxide clusters and/or the decomposition of nitric oxide on the cluster with the resulting loss of molecular nitrogen. [ABSTRACT FROM AUTHOR]

We report the observation of chemical reactions in gas-phase Rhn(N2O)m+ complexes driven by absorption of blackbody radiation. The experiments are performed under collision-free conditions in a Fourier transform ion cyclotron resonance mass spectrometer. Mid-infrared absorption by the molecularly adsorbed N2O moieties promotes a small fraction of the cluster distribution sufficiently to drive the N2O decomposition reaction, leading to the production of cluster oxides and the release of molecular nitrogen. N2O decomposition competes with molecular desorption and the branching ratios for the two processes show marked size effects, reflecting variations in the relative barriers. The rate of decay is shown to scale approximately linearly with the number of infrared chromophores. The experimental findings are interpreted in terms of calculated infrared absorption rates assuming a sudden-death limit. [ABSTRACT FROM AUTHOR]

Fourier transform ion cyclotron resonance mass spectrometry has been employed to study the reactions of gas-phase cationic cobalt clusters, Con+ (n=4–30), with nitric oxide, NO, and nitrous oxide, N2O, under single collision conditions. Isolation of the initial cluster permits detailed investigation of fragmentation channels which characterize the reactions of all but the largest clusters studied. In reaction with N2O, most clusters generate the monoxides ConO+ without fragmentation, cobalt atom loss accompanying only subsequent reactions. By contrast, chemisorption of even a single NO molecule is accompanied by fragmentation of the cluster. The measured rate coefficients for the Con++N2O reaction as a function of cluster size are significantly smaller than those calculated using the surface charge capture model, while for NO the rates are comparable. The reactions have been studied under high coverage conditions by storing clusters for extended periods to permit multiple reactions to occur. This leads to interesting chemistry on the surface of the cluster resulting in the formation of stable oxide clusters and/or the decomposition of nitric oxide on the cluster with the resulting loss of molecular nitrogen. [ABSTRACT FROM AUTHOR]

Broadbandcavity-enhanced absorption spectroscopy (BBCEAS) is shownto be a sensitive method for the detection of magnetic field effects(MFEs) in two flavin-based chemical reactions which are simple modelsfor cryptochrome magnetoreceptors. The advantages of optical cavity-baseddetection and (pseudo-white-light) supercontinuum radiation have beencombined to provide full spectral coverage across the whole of thevisible spectrum (425 < λ < 700 nm). This region coversthe absorbance spectra of flavin mononucleotide (FMN) and flavin adeninedinucleotide (FAD) as well as their photogenerated radicals. To illustratethe power of this technique, BBCEAS has been used to record the spectraldependence of MFEs for photoinduced radical pairs formed in the intermolecularreaction of FMN with lysozyme and the intramolecular photochemistryof FAD. These reactions have been chosen for their photochemical similaritiesto cryptochrome proteins which have been proposed as key to the magneticcompass sense of many animals including birds. In experiments performedusing low protein concentrations (10 μM) and 1 mm optical path-lengths,absorbance changes as small as 1 × 10–7(representing<0.1% MFEs) have been detected with good signal-to-noise offeringthe prospect of sensitive MFE detection in cryptochrome. [ABSTRACT FROM AUTHOR]

The reactions of nitrous oxide decoratedrhodium clusters, RhnN2O+(n= 5, 6), have been studied by Fouriertransform ion cyclotron resonancemass spectrometry. Collision induced dissociation with Ar is shownto lead to one of two processes; desorption of the intact N2O moiety (indicating molecular adsorption in the parent cluster)or N2O decomposition liberating molecular nitrogen withthe latter becoming increasingly dominant at higher collision energies.Consistent with the results of earlier studies, which employed infraredexcitation [Hermes, A. C.; et al.J. Phys. Chem. Lett. 2011, 2, 3053], Rh5ON2O+is observed to behave qualitatively differentlyto Rh5N2O+with decomposition ofthe nitrous oxide dominating the chemistry of the former. In otherexperiments, the reactivity of RhnN2O+clusters with CO has been studied. Chemisorptionof 13CO is calculated to deposit ca.2eV into the parent cluster, initiating a range of chemical processeson the cluster surface, which are fit to a simple reaction mechanism.Clear differences are again observed in the reaction branching ratiosfor Rh5N2O+and Rh6N2O+parent cluster ions. For the n= 5 cluster, the combined N2O reduction/CO oxidationis the most significant reaction channel, while the n= 6 cluster preferentially is oxidized to Rh6O+with loss of N2and CO. Even larger differences are observedin the reactions of the N2O decorated cluster oxides, RhnON2O+, for which morereaction possibilities arise. The results of all studies are discussedin relation to infrared driven processes on the same parent clusterspecies [Hamilton, S. M.; et al.J. Am. Chem. Soc.2010, 132, 1448; J. Phys.Chem. A, 2011, 115, 2489]. [ABSTRACT FROM AUTHOR]