Photoionization and ab initio study of Ba(H2O)n (n = 1 - 4) clusters

IVAN CABANILLAS-VIDOSA; MAXIMILIANO ROSSA; GUSTAVO A. PINO; JUAN C. FERRERO; CARLOS J. COBOS

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2012 vol. 14 p. 4276 - 4286

1463-9076

An experimental and a theoretical study of the photoionization energies (IE`s) of Ba(H2O)n clusters containing up to n = 4 water molecules has been performed. The clusters were generated by a pick-up source combining laser vaporization and pulsed supersonic expansion and photoionized by radiation of 272.5-340 nm. The experimentally determined IE`s values for n = 1 to 4 are (4.56 ± 0.05), (4.26 ± 0.05), (3.90 ± 0.05) and (3.71 ± 0.05) eV. This cluster size dependence of IE is reproduced within ± 0.06 eV employing the mPW1PW91 and CCSD(T, Full) quantum-chemical methods combined with the 6-311++G(d,p) basis set for the H and O atoms and three different relativistic effective core potentials for Ba atoms. The calculations indicate that the lowest energy hydration structures represent the most relevant contributions to both the vertical and adiabatic ionization energies. Experimental and theoretical evidences correlate with the progressive surface-delocalization of the electron from the hydration cavity around the Ba atom and suggest that the intra-cluster electron transfer is possible even for small aggregates.