Experimental and theoretical study of Penning ionisation of H2O by metastable helium He(23S)

Abstract
Combining experimental and theoretical information the authors develop a model for Penning ionisation of H2O by He(23S): the population ratio of the different ionic states depends on the orientation of H2O with respect to He*. A strong anisotropy of the He*+H2O energy surface makes this effect visible in the experimental electron energy spectrum.