Formation, photodissociation and structure of chromium/phosphorus binary cluster ions

Abstract

Chromium/phosphorus binary cluster ions, [Cr(n)P(m)](+/-), produced by laser (532nm) ablation on a tablet of well-mixed chromium and red phosphorus powder, were studied with a home-built tandem time-of-flight (TOF) mass spectrometer. The clusters thus formed are mostly rich in phosphorus. There is an odd-even oscillation in the intensity of the [CrP(m)](+) series, i.e. the mass peaks of even m are higher than those of odd m. The peaks of [CrP(4)](+) and [CrP(8)](+) are especially prominent, which may be ascribed to the specific stability of P(4) sub-structures. There are also some intense peaks in the spectrum assigned to [Cr(3)P(8)](+), [Cr(4)P(9)](+), [Cr(5)P(11)](+), [Cr(6)P(12)](+), [Cr(8)P(14)](+) clusters, etc., which have stable compositions. The stability of these species is consistent with a simple qualitative electronic structure model, in which the valence electrons of P are filled into the d orbitals of Cr. The photodissociation of some cluster ions was also studied. DFT calculations were performed on three small cluster ions to provide some insight into their structures. Copyright 2000 John Wiley & Sons, Ltd.