Formation of small negative and positive cluster ions of gold, silver, and copper by direct laser vaporization

Abstract

Direct laser vaporization techniques have been employed to produce small cluster cations and anions of gold, silver, and copper in a Fourier transform ion cylotron resonance mass spectrometer using pure metal samples. Aupn (p=+1 and −1, n=1–6), Ag+n (n=1–3), Ag−, Cu+n (n=1–3), and Cu−n (n=1–2) were observed, using two different experimental configurations. In one configuration ions were produced by Nd:YAG laser irradiation directed collinear with the magnetic field in the FTICR mass spectrometer while in the second laser light directed perpendicularly to the magnetic field was used. Relative kinetic energies of the aggregates, the relative intensities of positive vs negative ions, and the nature of the neutrals in the plasma formed by direct laser vaporization are discussed.