Showing papers by "Richard J. Saykally published in 2013"
TL;DR: Researchers show new evidence that the air side of the air/water interface is more basic than the aqueous one.
Abstract: The ability of the water surface to donate or accept protons critically influences vital processes in chemistry and biology, but intense disagreement persists regarding this property. Researchers show new evidence that the air side of the air/water interface is more basic than the aqueous one.
71 citations
TL;DR: Observed concentration-induced nitrogen K-edge resonance shifts result from π* state mixing and the release of water molecules from each first solvation sphere as two solvated guanidinium ions associate into a stacked pair configuration.
Abstract: The formation of like-charge guanidinium-guanidinium contact ion pairs in water is evidenced and characterized by X-ray absorption spectroscopy and first-principles spectral simulations based on molecular dynamics sampling. Observed concentration-induced nitrogen K-edge resonance shifts result from π* state mixing and the release of water molecules from each first solvation sphere as two solvated guanidinium ions associate into a stacked pair configuration. Possible biological implications of this counterintuitive cation-cation pairing are discussed.
64 citations
TL;DR: A combined theoretical and experimental study of the water octamer-h16 finds transitions appear as singlets, consistent with the instanton paths, which involve the breakage of two hydrogen-bonds and thus give tunneling splittings below experimental resolution.
Abstract: We report a combined theoretical and experimental study of the water octamer-h16. The calculations used the ring-polymer instanton method to compute tunnelling paths and splittings in full dimensionality. The experiments measured extensive high resolution spectra near 1.4 THz, for which isotope dilution experiments and group theoretical analysis support assignment to the octamer. Transitions appear as singlets, consistent with the instanton paths, which involve the breakage of two hydrogen-bonds and thus give tunneling splittings below experimental resolution.
57 citations
TL;DR: The presence of organic surfactants in atmospheric aerosol may lead to a depression of cloud droplet growth and evaporation rates affecting the radiative properties and lifetime of clouds, but the magnitude and mechanism of this effect remain poorly constrained.
Abstract: The presence of organic surfactants in atmospheric aerosol may lead to a depression of cloud droplet growth and evaporation rates affecting the radiative properties and lifetime of clouds. Both the magnitude and mechanism of this effect, however, remain poorly constrained. We have used Raman thermometry measurements of freely evaporating micro-droplets to determine evaporation coefficients for several concentrations of acetic acid, which is ubiquitous in atmospheric aerosol and has been shown to adsorb strongly to the air–water interface. We find no suppression of the evaporation kinetics over the concentration range studied (1–5 M). The evaporation coefficient determined for 2 M acetic acid is 0.53 ± 0.12, indistinguishable from that of pure water (0.62 ± 0.09).
29 citations
TL;DR: In this paper, the authors used liquid microjets and ultradilute solutions to overcome inherent difficulties in electrokinetic surface measurements engendered by changing double-layer thicknesses.
Abstract: We describe a novel method that exploits electrokinetic streaming current measurements for the study of ion-interface affinity. Through the use of liquid microjets and ultradilute solutions (<1 μM), we are able to overcome inherent difficulties in electrokinetic surface measurements engendered by changing double-layer thicknesses. Varying bulk KCl concentrations produce statistically significant changes in streaming current down at picomolar concentrations. Because the attending ion concentrations are below that from water autoionization, these data are compared with those from ultradilute HCl and KOH solutions assuming that the K+ and Cl– introduce no new counterions. This permits comparison of the individual effects of K+ and Cl– on the interface, evidencing a cooperative effect between these ions at silica surfaces. Altogether, these results establish the effectiveness of this experimental approach in revealing new ion–surface phenomena and indicate its promise for the general study of aqueous interfaces.
14 citations