The reduction of water clusters H+(H2O)n to (OH-)(H2O)m by double electron transfer from Cs atoms

(H+)(H2O)(n) ions (n = 1-72) at 50 keV energies were brought to collide with caesium atoms. The analysis of the products formed for clusters having n 4 4 shows that this leads to the formation of a population of (OH-)(H2O)(m) ions with a variable number m. On average, more than half of the water molecules are lost from the cluster in the process. A model can explain the experimental observations where two successive collisions occur within a time period of less than 100 ns. One-electron transfer from caesium to water leading to the loss of one hydrogen atom occurs at each stage. While the first stage is by itself exothermic, the second stage requires additional energy from collisional energy transfer.