Irene Rabin

Chemiluminescence in the Agglomeration of Metal Clusters

The agglomeration of copper or silver atoms in a matrix of noble gas atoms to form small clusters may be accompanied by the emission of visible light. Spectral analysis reveals the intermediate formation of electronically excited atoms and dimers as the source of the chemiluminescence. A mechanism is proposed, according to which the gain in binding energy upon cluster formation may even lead to the ejection of excited fragments as a result of unstable intermediate configurations. A similar concept was introduced in the field of nuclear reactions by Niels Bohr 60 years ago.

Fluorescence and excitation spectra of Ag4 in an argon matrix

We report the fluorescence and excitation spectra of size selected Ag4 deposited in an argon matrix. The main fluorescence peak for Ag4 is observed at 458 nm. The excitation spectrum for this emission is in good agreement with recent theoretical calculations and photodepletion experiments.

Absorption and fluorescence spectra of Ar-matrix-isolated Ag3 clusters

The absorption and fluorescence spectra of silver trimers isolated in an Ar matrix show the existence of three distinct lattice sites whereby the population of each site depends on the conditions of matrix preparation. Irradiation of certain absorption bands of the trimer isolated in one of these sites results in an irreversible reorganization of the surrounding matrix and population of another site. The experiments were performed with matrices prepared either by the matrix isolation/aggregation method or by soft landing of size-selected Ag/sub 3/ species.

LIGHT EMISSION DURING THE AGGLOMERATION OF SILVER CLUSTERS IN NOBLE GAS MATRICES

The agglomeration of small silver clusters in noble gas matrices to form larger ones may be accompanied by the emission of light. Spectral analysis reveals that part of radiation intensity can be attributed to fluorescence from excited metal atoms, dimers and trimers the formation of which results from cluster/cluster agglomeration as a consequence of the gain in binding energy. The remaining spectral features must be assigned to excited clusters Agn, with n⩾4.

Absorption spectra of small silver clusters Agn (n⩾3)

A novel preparation technique enables the generation of small silver clusters Agn in an argon matrix in the otherwise hardly accessible size range 3⩽n<40. Apart from the previously known absorption spectra around 350 nm, further bands at wavelengths up to 900 nm were detected. These features exhibit very low intensities and are attributed to low-energetic single electron–hole excitations.

Light emission in the agglomeration of silver clusters

Abstract Small noble-gas droplets are generated by adiabatic expansion and travel over a heated crucible where evaporated Ag atoms are picked up. The subsequent agglomeration of these Ag atoms to clusters is associated with light emission. This effect is caused by the gain in binding energy by the clustering process leading to the ejection, preferably, of excited trimers. The heat released by condensation and coagulation of the Ag atoms on the droplets causes continuous evaporation of the noble-gas atoms, so that under suitable conditions even light emission from the decay of free Ag 3 ∗ species could be observed and analyzed.