Water Network Shape-Dependence of Local Interactions with the Microhydrated -NO and -CO Anionic Head Groups by Cold Ion Vibrational Spectroscopy.

We report the structural evolutions of water networks and solvatochromic response of the CHNO radical anion in the OH and CH stretching regions by analysis of the vibrational spectra displayed by cryogenically cooled CHNO·(HO) clusters. The OH stretching bands evolve with a surprisingly large discontinuity at = 6, which features the emergence of an intense, strongly red-shifted band along with a weaker feature that appears in the region assigned to a free OH fundamental. Very similar behavior is displayed by the perdeuterated carboxylate clusters, RCO·(HO) (R = CDCD), indicating that this behavior is a general feature in the microhydration of the triatomic anionic domain and not associated with CH oscillators.

Characterization of the vibrational properties of copper difluoride anion and neutral ground states via direct and indirect photodetachment spectroscopy.

Photoelectron spectra of CuF are reported at wavelengths 310 nm, 346.6 nm, and 350.1 nm, obtained via velocity map imaging.

Heterogeneous Reactivity of Nitric Acid with Nascent Sea Spray Aerosol: Large Differences Observed between and within Individual Particles.

Current climate and atmospheric chemistry models assume that all sea spray particles react as if they are pure NaCl. However, recent studies of sea spray aerosol particles have shown that distinct particle types exist (including sea salt, organic carbon, and biological particles) as well as mixtures of these and, within each particle type, there is a range of single-particle chemical compositions. Because of these differences, individual particles should display a range of reactivities with trace atmospheric gases.

On the role of particle inorganic mixing state in the reactive uptake of N2O5 to ambient aerosol particles.

The rates of heterogeneous reactions of trace gases with aerosol particles are complex functions of particle chemical composition, morphology, and phase state. Currently, the majority of model parametrizations of heterogeneous reaction kinetics focus on the population average of aerosol particle mass, assuming that individual particles have the same chemical composition as the average state. Here we assess the impact of particle mixing state on heterogeneous reaction kinetics using the N2O5 reactive uptake coefficient, γ(N2O5), and dependence on the particulate chloride-to-nitrate ratio (nCl(-)/nNO3(-)).

Transition metal associations with primary biological particles in sea spray aerosol generated in a wave channel.

In the ocean, breaking waves generate air bubbles which burst at the surface and eject sea spray aerosol (SSA), consisting of sea salt, biogenic organic species, and primary biological aerosol particles (PBAP). Our overall understanding of atmospheric biological particles of marine origin remains poor. Here, we perform a control experiment, using an aerosol time-of-flight mass spectrometer to measure the mass spectral signatures of individual particles generated by bubbling a salt solution before and after addition of heterotrophic marine bacteria.

Inside versus outside: ion redistribution in nitric acid reacted sea spray aerosol particles as determined by single particle analysis.

Single particle analysis of individual sea spray aerosol particles shows that cations (Na(+), K(+), Mg(2+), and Ca(2+)) within individual particles undergo a spatial redistribution after heterogeneous reaction with nitric acid, along with the development of a more concentrated layer of organic matter at the surface of the particle. These data suggest that specific ion and aerosol pH effects play an important role in aerosol particle structure in ways that have not been previously recognized.

Size-dependent changes in sea spray aerosol composition and properties with different seawater conditions.

A great deal of uncertainty exists regarding the chemical diversity of particles in sea spray aerosol (SSA), as well as the degree of mixing between inorganic and organic species in individual SSA particles. Therefore, in this study, single particle analysis was performed on SSA particles, integrating transmission electron microscopy with energy dispersive X-ray analysis and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy, with a focus on quantifying the relative fractions of different particle types from 30 nm to 1 μm. SSA particles were produced from seawater in a unique ocean-atmosphere facility equipped with breaking waves.

Vibrational manifestations of strong non-Condon effects in the H3O(+)·X3 (X = Ar, N2, CH4, H2O) complexes: a possible explanation for the intensity in the "association band" in the vibrational spectrum of water.

The harmonic approximation provides a powerful approach for interpreting vibrational spectra. In this treatment, the energy and intensity of the 3N- 6 normal modes are calculated using a quadratic expansion of the potential energy and a linear expansion of the dipole moment surfaces, respectively. In reality, transitions are often observed that are not accounted for by this approach (e.

Bottom-up view of water network-mediated CO2 reduction using cryogenic cluster ion spectroscopy and direct dynamics simulations.

The transition states of a chemical reaction in solution are generally accessed through exchange of thermal energy between the solvent and the reactants. As such, an ensemble of reacting systems approaches the transition state configuration of reactant and surrounding solvent in an incoherent manner that does not lend itself to direct experimental observation. Here we describe how gas-phase cluster chemistry can provide a detailed picture of the microscopic mechanics at play when a network of six water molecules mediates the trapping of a highly reactive "hydrated electron" onto a neutral CO(2) molecule to form a radical anion.

NH+-F hydrogen bonding in a fluorinated "proton sponge" derivative: integration of solution, solid-state, gas-phase, and computational studies.

We report detailed studies on the characterization of an intramolecular NH-F hydrogen bond formed within a fluorinated "proton sponge" derivative. An ammonium ion, generated from 8-fluoro-N,N-dimethylnaphthalen-1-amine, serves as a charged hydrogen bond donor to a covalently bound fluorine appropriately positioned on the naphthalene skeleton. Potentiometric titrations of various N,N-dimethylnaphthalen-1-amines demonstrate a significant increase in basicity when hydrogen bonding is possible.

Unraveling anharmonic effects in the vibrational predissociation spectra of H5O2(+) and its deuterated analogues.

The nature of anharmonic couplings in the H(5)O(2)(+) "Zundel" ion and its deuterated isotopologues is investigated through comparison of their measured and calculated vibrational spectra. This follows a recent study in which we reported spectra for H(5)O(2)(+), D(5)O(2)(+), and D(4)HO(2)(+) from ∼600 to 4000 cm(-1), as well as H(4)DO(2)(+) in the OH and OD stretching regions [ J. Phys.

Survey of Ar-tagged predissociation and vibrationally mediated photodetachment spectroscopies of the vinylidene anion, C2H2-.

We report predissociation spectra of Ar-tagged C(2)H(2)(-) and C(2)D(2)(-) anions, and explore vibrationally mediated photodetachment from various vibrational levels of the bare C(2)H(2)(-) ion using velocity-map imaging. Intense photodetachment resonances are observed in the C-H stretching region that are strongly correlated with vibrational hot bands in the anion photoelectron spectra, indicating that one-color, resonant two-photon photodetachment (R2PD) is complicated by excitation of vibrationally excited states with autodetaching upper levels embedded in the continuum. Isolation of the R2PD spectrum was achieved using a two-color, IR-IR scheme in which vibrational excitation and photodetachment were carried out in two separate laser interaction regions.

How the shape of an H-bonded network controls proton-coupled water activation in HONO formation.

Many chemical reactions in atmospheric aerosols and bulk aqueous environments are influenced by the surrounding solvation shell, but the precise molecular interactions underlying such effects have rarely been elucidated. We exploited recent advances in isomer-specific cluster vibrational spectroscopy to explore the fundamental relation between the hydrogen (H)-bonding arrangement of a set of ion-solvating water molecules and the chemical activity of this ensemble. We find that the extent to which the nitrosonium ion (NO+)and water form nitrous acid (HONO) and a hydrated proton cluster in the critical trihydrate depends sensitively on the geometrical arrangement of the water molecules in the network.

Isolating the spectra of cluster ion isomers using Ar-"tag" -mediated IR-IR double resonance within the vibrational manifolds: Application to NO2- *H2O.

We demonstrate a method for isolating the vibrational predissociation spectra of different structural isomers of mass-selected cluster ions based on a population-labeling double resonance scheme. This involves a variation on the "ion dip" approach and is carried out with three stages of mass selection in order to separate the fragment ion signals arising from a fixed-frequency population-monitoring laser and those generated by a scanned laser that removes population of species resonant in the course of the scan. We demonstrate the method on the Ar-tagged NO(2) (-)H(2)O cluster, where we identify the spectral patterns arising from two isomers.

Probing isomer interconversion in anionic water clusters using an Ar-mediated pump-probe approach: Combining vibrational predissociation and velocity-map photoelectron imaging spectroscopies.

We present the first results from an experiment designed to explore barriers for interconversion between isomers of cluster anions using an Ar-cluster mediated pump-probe technique. In this approach, anions are generated with many Ar atoms attached, and one of the isomers present is selectively excited by tuning an infrared laser to one of the isomer's characteristic vibrational resonances. The excited cluster is then cooled by evaporation of Ar atoms, and the isomer distribution in the lighter daughter ions is measured after secondary mass selection by recording their photoelectron spectra using velocity-map imaging.