The chemistry of Sr2+ in association with propanol clusters

A combination of the 'pick-up' technique and high resolution mass spectrometric methods have been used to generate and study doubly charged cluster ions of the form [Sr(CH3CH2CH2OH)(n)](2+). As a result of charge transfer, no ions are observed for n = 1 and the parent ion distribution rises to a sharp maximum at n = 4, suggesting a first solvation shell. For n = 2 the parent ion is observed to undergo charge transfer via unimolecular (metastable) decay to give Sr+OH(C3H7OH) as the principal fragment with a significant fraction of the Coulomb energy appearing as kinetic energy release. Larger parent ions exhibit propanol loss as the dominant metastable decay channel. In contrast, the collisional activation of [Sr(C3H7OH)(n)](2+) ions for n > 2 is observed to promote extensive fragmentation accompanied by Coulomb explosion in which charged separation follows the breaking of covalent bonds. However, in some instances the measured kinetic energy releases for the latter process are very much lower than expected and it is suggested that either excess energy is being carried away by very light fragments, e.g. H and H-2, or that the energy available is low due to small differences in the ionisation energies of the product ions. Reaction products observed for [Sr(C3H7OH)(n)](2+) ions can be accounted for by assuming anion transfer processes. (C) 1997 Elsevier Science B.V.