Photoelectron spectra of the negative ions Ni(CO)"-, = 1-3, obtained with a fixed-frequency argon-ion laser operating at 488 nm are reported. The spectra provide the electron affinities for this series, EA[Ni(CO)] = 0.804 ± 0.012 eV, EA[Ni(CO)2] = 0.643 ± 0.014 eV, and EA[Ni(CO)3] = 1.077 ± 0.013 eV. The symmetric C-0 vibrational frequencies for the neutral complexes are obtained from the spectra. Metal-carbonyl bond strengths for the neutral carbonyls, Ni(CO)", = 1-4, are derived from these and other data. Electronic and geometric structure of ions and neutrals is also discussed.

The photoelectron spectra of 11 transition metal negative ions have been obtained in a crossed beam experiment using a sputter type ion source and a fixed frequency ArII laser (488 nm). The electron affinities (E.A.’s) are measured to be E.A.(Ti)=0.080±0.014 eV, E.A.(V)=0.526±0.012 eV, E.A.(Cr)=0.667±0.010 eV, E.A.(Zr)=0.427±0.014 eV, E.A.(Nb) =0.894±0.025 eV, E.A.(Mo)=0.747±0.010 eV, E.A.(Rh)=1.138±0.008 eV, E.A.(Pd)=0.558±0.008 eV, E.A.(Ta)=0.323±0.012 eV, E.A.(W)=0.816±0.008 eV, and E.A.(Ir)=1.566±0.008 eV. The ground states of the negative ions of these elements are determined from analysis of the photoelectron spectra and all are found to be of a dks2 configuration with the exception of Pd−(d10 s). Excited electronic states of Pd−[(4d95s2) 2D5/2] and Ta−[(5d46s2) 3P0] are identified. Calculation of relative intensities of photelectron transitions is used extensively in the analysis of the spectra and is compared with experiment for a number of cases. The spin–orbit separations for Rh−(3F) and Ta−(5D) are measured and compared with values obtained from ratio isoelectronic extrapolation. The accuracy of this extrapolation technique is discussed and an extensive table of extrapolated splittings for transition metal negative ions is given. Plots of the s-electron binding energies of the transition metal negative ions versus the number of d electrons exhibit smooth trends and striking similarities for each of the three transition series.

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The evolution of droplet temperatures in an electrospray plume was measured via ratiometric fluorescence. Under typical operating conditions, droplet temperatures decrease ∼30 K over the first 5.0 mm along the spray axis, followed by a slight (∼2-3 K) rewarming. Experimental axial profiles (Z-axis) were fit by use of diffusion-controlled and surface-controlled evaporation models. Both models fit the experimental data well for the cooling portion of the spray (Pearson correlation coefficient R ≥ 0.994), but the surface-controlled model required unrealistic droplet radius values to obtain a good fit. In lateral profiles at a given Z near the emitter tip, temperatures are lower (by 3.0-10 K) in the periphery than on the spray axis. This behavior is consistent with the expected enrichment of the spray periphery with smaller droplets. At longer axial distances, lateral profiles were relatively flat. Droplet temperature as a function of axial displacement fell more rapidly at lower liquid flow rates, possibly attributable to changes in droplet size and/or velocity with flow rate.

In this study we investigate the formation of non-covalent electron donor-acceptor (EDA) interactions between polymers and single-walled carbon nanotubes (SWNTs) with the goal of optimizing interfacial adhesion and homogeneity of nanocomposites without modifying the SWNT native surface. Nanocomposites of SWNTs and three sets of polymer matrices with varying composition of electron donating 2-(dimethylamino)ethyl methacrylate (DMAEMA) or electron accepting acrylonitrile (AN) and cyanostyrene (CNSt) were prepared, quantitatively characterized by optical microscopy and Raman spectroscopy (Raman mapping, Raman D* peak shifts) and qualitatively compared through thick film composite visualization. The experimental data show that copolymers with 30 mol% DMAEMA, 45 mol% AN, 23 mol% CNSt and polyacrylonitrile homopolymer have the highest extent of intermolecular interaction, which translates to an optimum SWNT spatial dispersion among the series. These results are found to correlate very well with the intermolecular interaction energies obtained from quantum density functional theory calculations. Both experimental and computational results also illustrate that chain connectivity is critical in controlling the accessibility of the functional groups to form intermolecular interactions. This means that an adequate distance between interacting functional groups on a polymer chain is needed in order to allow efficient intermolecular contact. Thus, controlling the amount of electron donating or withdrawing moieties throughout the polymer chain will direct the extent of EDA interaction, which enables tuning the SWNT dispersion.

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A sputter ion source has been used to obtain beams of B−, Al−, Bi−, and Pb− ions. A mass analyzed beam of each of these ions was crossed with a fixed frequency argon ion laser operating at 488 nm, and a photoelectron spectrum obtained at a resolution of 60 meV. From an analysis of these data the following electron affinities were obtained: B, 0.278±0.010 eV; Al, 0.442±0.010 eV; Bi, 0.947±0.010 eV; Pb, 0.365±0.008 eV. In addition, a1D excited state of Al− was observed 0.332±0.010 eV above the ground state of the negative ion.

Mixed clusters of the form (NO)mArn(m ≤ 4,n ≤ 22)are produced in a supersonic expansion and photoionized by nonresonant two-photon absorption of 266 nm photons. The ions are subsequently separated and detected by time-of-flight mass spectrometry. Anomalously large relative intensities are observed for the cluster ions, NO+Arn(n= 12,18,22) and (NO)2+Arn(n = 17,21), and are attributed to extra stability of these ions. These ‘‘magic numbers’’ at (m+n)=13,19,23 are compared to those observed in rare gas clusters and other M+Arn heteroclusters and assigned to icosahedral structures. Other cluster ions of the form (NO)+mNO2, (NO)+mN2O, N2O+Arn, and (NO)+mH2O are observed and briefly discussed.