Protonated water clusters and their black body radiation induced fragmentation

Protonated water clusters H+(H2O)(n), n = 5,...,65 and their perdeuterated analogues were produced in a discharge source and stored in an electromagnetic ICR-ion trap under collision-free conditions. The rates of their fragmentation or 'evaporation' due to absorption of the 300 K black body background radiation exhibit an overall tau similar to 1/n dependence. Local deviations of some clusters (e.g. n = 21 or 55) from the overall trend are attributed to their higher stabilities. The fragmentation is modeled by extrapolating macroscopic water droplet evaporation to the microscopic clusters.