Search

Series of time-resolved still images of the explosion dynamics of micrometer-sized water droplets after femtosecond laser-pulse irradiation were obtained for different laser-pulse intensities. Amplified pulses centered around a wavelength of 805 nm with 1-mJ energy and 60-fs duration were focused onto the droplet to initiate the dynamics. Several effects, such as forward and backward plumes, jets, water films, and shock waves, were investigated. Additionally, the influence of different pulse durations produced by chirping the laser pulses was observed. OCIS codes: 320.0320, 190.3970, 320.7120.

Reactions of free silver anions Ag[sub n][sup -] (n=1–13) with O[sub 2], CO, and their mixtures are investigated in a temperature controlled radio frequency ion trap setup. Cluster anions Ag[sub n][sup -] (n=1–11) readily react with molecular oxygen to yield Ag[sub n]O[sub m][sup -] (m=2, 4, or 6) oxide products. In contrast, no reaction of the silver cluster anions with carbon monoxide is detected. However, if silver cluster anions are exposed to the mixture of O[sub 2] and CO, new reaction products and a pronounced, discontinuous size dependence in the reaction behavior is observed. In particular, coadsorption complexes Ag[sub n](CO)O[sub 2][sup -] are detected for cluster sizes with n=4 and 6 and, the most striking observation, in the case of the larger odd atom number clusters Ag[sub 7][sup -], Ag[sub 9][sup -], and Ag[sub 11][sup -], the oxide product concentration decreases while a reappearance of the bare metal cluster signal is observed. This leads to the conclusion that carbon monoxide reacts with the activated oxygen on these silver clusters and indicates the prevalence of a catalytic reaction cycle. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Mass spectra and kinetic measurements that reveal an unprecedented size dependence in the adsorption of multiple oxygen molecules onto anionic silver clusters are presented. These findings of coadsorption properties on Agn- clusters are conceptually important for the understanding of the role of silver clusters in oxidation processes.

Temperature-dependent rf-ion trap mass spectrometry and first-principles simulations reveal the detailed reaction mechanism of the catalytic gas-phase oxidation of CO by free Au[sub 2, sup -] ions in the presence of O[sub 2]. A metastable intermediate with a mass of Au[sub 2]CO[sub 3, sup -] was observed at low temperatures. Two alternative structures corresponding to digold carbonate or peroxyformate are predicted for this intermediate. Both structures are characterized by low activation barriers for the formation of CO[sub 2]. These combined experimental and theoretical investigations provide a comprehensive understanding of the kinetics, energetics, and atomic arrangements along the reaction path, thus allowing a formulation of the catalytic cycle for the oxidation reaction. [ABSTRACT FROM AUTHOR]