Swarm experiment on ionized water clusters

Drift of positively ionized water clusters formed in a low-pressure electri cal discharge was studied by mass spectroscopy. Ions H+(H2O)(n) with n = 1- 7 were observed at room temperature and at pressures in a few hundreds Pa r ange. Relative cluster abundances depend on the reduced electrical field in the drift chamber. The H+(H2O)(4) clusters are somewhat more abundant than those with n = 3.5. Fragmentation energies, in a rough agreement with othe r experimental and theoretical values, have been derived from equilibrium c onditions for relative cluster abundances. Calculations of dissociation ene rgies of cationic clusters with n up to 7 have been performed in Hartree-Fo ck approximation with a 6-311**G basis set. (C) 2001 Elsevier Science B.V.