Hydration of halide and bromine negative ions in a supersonic jet expansion

Abstract

The water cluster ions, X − (H 2 O) n , where X − = F − , Cl − , Br − , or I − and n = 1−24, are observed within a supersonic free jet expansion of moist argon buffer gas by an atmospheric pressure ionization mass spectrometer. The relative intensities of these ions suggest the existence of special stabilities for certain large cluster ions containing 10 or more water molecules. The magnitudes of these special stabilities increase with decreasing size of the core ion so that they are most distinct for clusters of F − and not detectable for those of I − . Special stabilities are also observed for relatively large water clusters of bromine negative ion, Br − 2 (H 2 O) n .