Unexpected size distribution of Ba(H2O)n clusters: why is the intensity of the Ba(H2O)1 cluster anomalous low?

IVÁN CABANILLAS-VIDOSA; MAXIMILIANO ROSSA; GUSTAVO A. PINO; JUAN C. FERRERO

ROYAL SOC CHEMISTRY

Año: 2011 vol. 13 p. 13387 - 13387

n experimental and theoretical study on the reactivity of neutral Ba atoms with water clusters has been conducted to unravel the origin of the irregular intensity pattern observed in one-photon ionization mass spectra of a Ba(H2O)n / BaOH(H2O)n1 (n = 1-4) cluster distribution, which was generated in a laser vaporization-supersonic expansion source. The most remarkable irregular feature is the finding for n = 1 of a lower intensity for the Ba+(H2O)n peak with respect to that of BaOH+(H2O)n1, which is opposite to the trend for n = 2-4. Rationalization of the data required consideration of a distinct behavior of ground-state and electronically excited state Ba atoms in inelastic and reactive Ba + (H2O)n encounters that can occur in the cluster source. Within this picture, the generation of Ba(H2O)n (n  1) association products results from stabilizing collisions with atoms of the carrier gas, which are favored by intramolecular vibrational redistribution that opera