We report on the time evolution of the sodium tetrachloroaurate (NaAuCl(4)) chemical properties as a function of soft X-ray exposure in a dried sample on a silicon surface using X-ray photoelectron spectroscopy (XPS). Our investigations provide mechanistic insight into the photoreduction kinetics from Au(III) to Au(I) and then Au(I) to Au(0). We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au(I) state. Both photoreduction steps undergo first-order kinetics.

We report on the time evolution of gold nanoparticle (AuNP) optical properties and size distributions as a function of laser irradiation in pure water samples and at sodium dodecylsulphate (SDS) surfactant concentrations above and below the SDS critical micelle concentration in water. Our investigations provide a mechanistic insight into the laser-induced formation kinetics involved in AuNP production via 1064 nm laser irradiation in aqueous solution, as well as the relative stabilities of different AuNP size regimes. Following preparation via laser ablation at 1064 nm, we show that 532 nm laser irradiation in the absence of surfactant generates AuNP that are both small in size and possess a narrow particle size distribution. This distribution remains narrow and shifts to smaller average particle size with increasing surfactant concentration.

We report on the time evolution of gold nanoparticles produced by laser ablation in the presence of the cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) in aqueous solution. The broader applicability of a laser-induced nanoparticle formation kinetic model previously developed by us for the case of anionic surfactants in aqueous solution [ J. Phys. Chem. C 2010 , 114 , 15931 - 15940 ] is shown to also apply in the presence of cationic surfactants. We explore the surface properties of the nanoparticles produced in the presence of the cationic surfactants via synchrotron X-ray photoelectron spectroscopy (XPS). The XPS data indicate that at CTA(+) concentrations approximating the aqueous critical micelle concentration Au(III) is present on the nanoparticle surface. Such oxidation is not observed at (i) lower CTA(+) concentrations, (ii) in the presence of an anionic surfactant, or (iii) in the case of pure water as a solvent.

Photoelectron spectra following photodetachment of the gold dicarbide anion, ${\rm AuC}_2^ - $ AuC 2−, have been recorded using the velocity map imaging technique at several excitation wavelengths. The binding energy spectra show well-defined vibrational structure which, with the aid of computational calculations and Franck-Condon simulations, was assigned to a progression in the Au–C stretching mode, ν3. The experimental data indicate that the features in the spectrum correspond to a 2A′ ← 3A′ transition, involving states which we calculate to have bond angles ∼147° but with a low barrier to linearity.

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Abstract. We have developed a novel single-beam photothermal interferometer and present here its application for the measurement of aerosol light absorption. The use of only a single laser beam allows for a compact optical set-up and significantly easier alignment compared to standard dual-beam photothermal interferometers, making it ideal for field measurements. Due to a unique configuration of the reference interferometer arm, light absorption by aerosols can be determined directly – even in the presence of light-absorbing gases. The instrument can be calibrated directly with light-absorbing gases, such as NO2, and can be used to calibrate other light absorption instruments. The detection limits (1σ) for absorption for 10 and 60 s averaging times were determined to be 14.6 and 7.4 Mm−1, respectively, which for a mass absorption cross section of 10 m2 g−1 leads to equivalent black carbon concentration detection limits of 1460 and 740 ng m−3, respectively. The detection limit could be reduced further by improvements to the isolation of the instrument and the signal detection and processing schemes employed.

The available knowledge of the electronically excited states of the copper dimer is limited. This is common for transition metals, as the high density of states hinders both experimental assignment and computation. In this work, two-color resonant four-wave mixing spectroscopy was applied to neutral Cu in the gas phase. The method yielded accurate positions of individual rovibrational lines in the I-X and J-X electronic systems. This revealed the term symbols for the I and J states as Π (1) and Σ (0), respectively. For the Cu isotopologue, accurate molecular constants were obtained. The characterization of the J state finally allowed decisive determination of its electron configuration. The J state is obtained from the ground state by promotion of a 3dπ electron into the weakly bonding 4pπ molecular orbital. From the data analysis, lifetimes of the I state (between 10 ps and 5 ns) and J state (66 ns) were inferred.

The potential of two-color resonant and degenerate four-wave mixing spectroscopy for investigations of the complex spectra of transition metal dimers is explored. Two-color resonant and degenerate four-wave mixing spectroscopy scans of the well-known A-X and B-X transitions in Cu 2 are reported and compared with previous experimental data obtained from standard singleresonance techniques. The selectivity of the method is shown to enable the measurement of isotopologue pure spectra without the need for isotopically enriched metal targets. Specific subsets of the rovibronic structure are separated in a congested spectral region of overlapping transitions. The sensitivity of the method compares satisfactorily with linear spectroscopic methods such as laser-induced fluorescence and cavity ring-down. A new laser vaporization source for the production of transition metal dimers and clusters has been constructed. The new design aims for a high number density and maximum possible shot-to-shot stability. The possibilities of further applications of non-linear four-wave mixing spectroscopy to Cu 2 and other transition metal dimers are discussed.