Formation of Ca-O clusters and their protonation and hydration in direct laser vaporization

Calcium oxide clusters produced in the direct laser vaporization of different precursor solid samples CaO, Ca(OH)(2) and CaCO3 have been investigated by a time-of-flight mass spectrometer. Besides [Ca(CaO)(n)](+) and [(CaO)(n)](+) clusters, considerable protonated clusters [H(CaO)(n)](+) and hydrated clusters [H(CaO)(n)(H2O)(m)](+) have also been found in the TOF mass spectra. The characteristic of the abundance distribution of the clusters shows that the formation process of calcium oxide clusters should proceed along the growth course of the rock salt structure, which is further supported by the reactivity of [H(CaO)(n)](+) clusters with H2O produced in the direct laser vaporization.