Surface-induced dissociation from a liquid surface

Mass-selected projectile ions in the tens of electronvolt energy range undergo surface-induced dissociation upon collision with a liquid perfluorinated polyether (PFPE) surface. The efficiency of translational-to-vibrational (T-V) energy transfer is simiar to that observed for a fluorinated self-assembled monolayer (SAM) surface. The thermometer ion W(CO)+·6 was used to determine an average T-V conversion efficiency of 18% in the collision energy range of 30-50 eV. The surface can be bombarded for several hours without displaying any change in the scattered ion products. Ion-surface reactions occur with some projectiles and are analogous to those seen with the fluorinated SAM surface. For example WF+| (m = 1-5) and W(CO)nF+| (n = 1-2, m = 1-2) are generated upon collisions of W(CO)+·6 with the PFPE liquid surface. The ion-surface reactions observed suggest that F atoms and / or CF3 groups are accessible for reaction while the oxygen atoms lie below the outermost surface layer. Chemical sputtering of the liquid surface also occurs and yields common fluorocarbon fragment ions, including CF+3, C2F+7 and the oxygenated product CFO+. The liquid surface is remarkably free of hydrocarbon impurities. Collisions of the pyrazine and benzene molecular ions, both probes for hydrocarbon impurities, resulted in very little protonated pyrazine or protonated benzene

Gas-phase C-F bond cleavage in perfluorohexane using W-, Si-, P-, Br-, and I-containing ions: comparisons with reactions at fluorocarbon surfaces

Gas-phase reactions of W-, Si-, P-, Br-, and I-containing ions with the target molecule perfluorohexane at low collision energies (<15 eV) parallel known ion/surface reactions of the same projectile ions at fluorinated self-assembled monolayer surfaces. Charge exchange, dissociative charge exchange, and fluorine atom abstraction are observed and the majority of the projectile ions also undergo reactive charge exchange to produce specific fluorocarbon fragment ions of the target molecule in distinctive relative abundances. Abstraction of up to five fluorine atoms is observed upon collision of W+ with gaseous perfluorohexane, while similar experiments with CI+, SiCl+, and PCl+· show abstraction of one or two fluorine atoms. Other projectiles, including Si+·, PCl2+, Br+, CBr+, and I+, abstract only a single fluorine atom. These patterns of fluorine atom abstraction are similar to those observed in ion/surface collisions. Also paralleling the ion/surface reactions, halogen exchange (Cl-for-F) reactions occur between the Cl-containing projectile ions and perfluorohexane to produce C6F12Cl+, a product of chemical modification of the target. Collisions of PCl+. and PCl2+ also result in production of C6F12+·, indicating that the corresponding surface modification reaction involving molecular defluorination should be sought. Implications for previously proposed mechanisms, new ion/surface reactions, and for the use of gas-phase studies to guide investigations of the ion/surface reactions are discussed

Metastable anions of dinitrobenzene: resonances for electron attachment and kinetic energy release

Attachment of free, low-energy electrons to dinitrobenzene (DNB) in the gas phase leads to DNB as well as several fragment anions. DNB, (DNB-H), (DNB-NO), (DNB-2NO), and (DNB-NO(2)) are found to undergo metastable (unimolecular) dissociation. A rich pattern of resonances in the yield of these metastable reactions versus electron energy is observed; some resonances are highly isomer-specific. Most metastable reactions are accompanied by large average kinetic energy releases (KER) that range from 0.5 to 1.32 eV, typical of complex rearrangement reactions, but (1,3-DNB-H)(-) features a resonance with a KER of only 0.06 eV for loss of NO. (1,3-DNB-NO)(-) offers a rare example of a sequential metastable reaction, namely, loss of NO followed by loss of CO to yield C(5)H(4)O(-) with a large KER of 1.32 eV. The G4(MP2) method is applied to compute adiabatic electron affinities and reaction energies for several of the observed metastable channels. (C) 2010 American Institute of Physics. [doi:10.1063/1.3514931

Coulomb fission in multiply charged molecular clusters: experiment and theory

A series of three multiply charged molecular clusters, (C6H6)nz+ (benzene), (CH3CN)nz+ (acetonitrile), and (C4H8O)nz+ (tetrahydrofuran), where the charge z is either 3 or 4, have been studied for the purpose of identifying patterns of behaviour close to the charge instability limit. Experiments show that on a time scale of ~10-4 s, ions close to the limit undergo Coulomb fission where all of the observed pathways exhibit considerable asymmetry in the sizes of the charged fragments, and are associated with kinetic (ejection) energies of between 1.4 and 2.2 eV. Accurate kinetic energies have been determined through a computer simulation of peak profiles recorded in the experiments and the results modelled using a theory formulated to describe how charged particles of dielectric materials interact with one another (Bichoutskaia et al. J. Chem. Phys. 2010, 133, 024105). The calculated electrostatic interaction energy between separating fragments gives an accurate account for the measured kinetic energies and also supports the conclusion that +4 ions fragment into +3 and +1 products as opposed to the alternative of two +2 fragments. This close match between theory and experiment supports the assumption that a significant fraction of excess charge resides on the surfaces of the fragment ions. It is proposed that the high degree of asymmetry seen in the fragmentation patterns of the multiply charged clusters is due, in part, to limits imposed by the time window during which observations are made

Differentiation of Prostate Cancer from Normal Tissue in Radical Prostatectomy Specimens by Desorption Electrospray Ionization and Touch Spray Ionization Mass Spectrometry.

Radical prostatectomy is a common treatment option for prostate cancer before it has spread beyond the prostate. Examination for surgical margins is performed post-operatively with positive margins reported to occur in 6.5 – 32% of cases. Rapid identification of cancerous tissue during surgery could improve surgical resection. Desorption electrospray ionization (DESI) is an ambient ionization method which produces mass spectra dominated by lipid signals directly from prostate tissue. With the use of multivariate statistics, these mass spectra can be used to differentiate cancerous and normal tissue. The method was applied to 100 samples from 12 human patients to create a training set of MS data. The quality of the discrimination achieved was evaluated using principal component analysis - linear discriminant analysis (PCA-LDA) and confirmed by histopathology. Cross validation (PCA-LDA) showed >95% accuracy. An even faster and more convenient method, touch spray (TS) mass spectrometry, not previously tested to differentiate diseased tissue, was also evaluated by building a similar MS data base characteristic of tumor and normal tissue. An independent set of 70 non-targeted biopsies from six patients was then used to record lipid profile data resulting in 110 data points for an evaluation dataset for TS-MS. This method gave prediction success rates measured against histopathology of 93%. These results suggest that DESI and TS could be useful in differentiating tumor and normal prostate tissue at surgical margins and that these methods should be evaluated intra-operatively

Whiteness, Blackness and Settlement: Leisure and the Integration of New Migrants

At times of economic uncertainty the position of new migrants is subject to ever closer scrutiny. While the main focus of attention tends to be on the world of employment the research on which this paper is based started from the proposition that leisure and sport spaces can support processes of social inclusion yet may also serve to exclude certain groups. As such, these spaces may be seen as contested and racialised places that shape behaviour. The paper draws on interviews with White migrants from Poland and Black migrants from Africa to examine the normalising of whiteness. We use this paper not just to explore how leisure and sport spaces are encoded by new migrants, but how struggles over those spaces and the use of social and cultural capital are racialised