Superoxide formation on isolated cationic gold clusters.

Gold nanoparticles are known to be highly versatile oxidation catalysts utilizing molecular oxygen as a feedstock, but the mechanism and species responsible for activating oxygen remain unclear. The reaction between unsupported cationic gold clusters and molecular oxygen has been investigated. The resulting complexes were characterized in the gas phase using IR spectroscopy.

Structure assignment, electronic properties, and magnetism quenching of endohedrally doped neutral silicon clusters, Si(n)Co (n = 10-12).

The structures of neutral cobalt-doped silicon clusters have been assigned by a combined experimental and theoretical study. Size-selective infrared spectra of neutral Si(n)Co (n = 10-12) clusters are measured using a tunable IR-UV two-color ionization scheme. The experimental infrared spectra are compared with calculated spectra of low-energy structures predicted at the B3P86 level of theory.

The geometric structure of silver-doped silicon clusters.

Cationic silver-doped silicon clusters, Si(n)Ag(+) (n=6-15), are studied using infrared multiple photon dissociation in combination with density functional theory computations. Candidate structures are identified using a basin-hopping global optimizations method. Based on the comparison of experimental and calculated IR spectra for the identified low-energy isomers, structures are assigned.

Charge separation promoted activation of molecular oxygen by neutral gold clusters.

Gold nanoparticles and sub-nanoparticles famously act as highly efficient and selective low-temperature oxidation catalysts with molecular oxygen, in stark contrast to the nobility of the bulk phase. The origins of this activity and the nature of the active species remain open questions. Gas-phase studies of isolated gold clusters hold promise for disentangling these problems.

Xe+ formation following photolysis of Au-Xe: a velocity map imaging study.

The photodissociation dynamics of Au-Xe leading to Xe(+) formation via the Ξ(1∕2)-X(2)Σ(+) (v('), 0) band system (41 500-41 800 cm(-1)) have been investigated by velocity map imaging. Five product channels have been indentified, which can be assigned to photoinduced charge transfer followed by photodissociation in either the neutral or the [Au-Xe](+) species. For the neutral species, charge transfer occurs via a superexcited Rydberg state prior to dissociative ionization, while single-photon excitation of the gold atom in Au(+)-Xe accesses an (Au(+))∗-Xe excited state that couples to a dissociative continuum in Au-Xe(+).

A velocity map imaging study of gold-rare gas complexes: Au-Ar, Au-Kr, and Au-Xe.

The ultraviolet photodissociation dynamics of the gold-rare gas atom van der Waals complexes (Au-RG, RG = Ar, Kr, and Xe) have been studied by velocity map imaging. Photofragmentation of Au-Ar and Au-Kr at several wavelengths permits extrapolation to zero of the total kinetic energy release (TKER) spectra as monitored in the Au((2)P(3/2)(o)[5d(10)6p]) fragment channel, facilitating the determination of ground state dissociation energies of D(0)(")(Au-Ar) = 149+/-13 cm(-1) and D(0)(")(Au-Kr) = 240+/-19 cm(-1), respectively. In the same spectral region, transitions to vibrational levels of an Omega(') = 1/2 state of the Au-Xe complex result in predissociation to the lower Au((2)P(1/2)(o)[5d(10)6p])+Xe((1)S(0)[5p(6)]) fragment channel for which TKER extrapolation yields a value of D(0)(")(Au-Xe) = 636+/-27 cm(-1).