title: Heat capacities of freely evaporating charged water clusters.
abstract: We report on evaporation studies on positively charged water clusters (H(+)(H(2)O)(N)) and negatively charged mixed clusters (X(-)(H(2)O)(N)) with a small core ion X (X=O(2), CO(3), or NO(3)), in the size range N=5-300. The clusters were produced by corona discharge in ambient air, accelerated to 50 keV and mass selected by an electromagnet. The loss of monomers during the subsequent 3.4 m free flight was recorded. The average losses are proportional to the clusters' heat capacities and this allowed the determination of size-dependent heat capacities. The values are found to increase almost linearly with clusters size for both species, with a rate of 6k(B)-8k(B) per added molecule. For clusters with N<21 the heat capacities per molecule are lower but the incremental increase higher. For N>21 the values are intermediate between the bulk liquid and the solid water 0 degrees C values.
authors.affiliation: Department of Physics, University of Gothenburg, 41296 Gothenburg, Sweden.
authors.forename: A E K
authors.initials: AE
authors.lastname: Sundén
authors.forename: K
authors.initials: K
authors.lastname: Støchkel
authors.forename: S
authors.initials: S
authors.lastname: Panja
authors.forename: U
authors.initials: U
authors.lastname: Kadhane
authors.forename: P
authors.initials: P
authors.lastname: Hvelplund
authors.forename: S Brøndsted
authors.initials: SB
authors.lastname: Nielsen
authors.forename: H
authors.initials: H
authors.lastname: Zettergren
authors.forename: B
authors.initials: B
authors.lastname: Dynefors
authors.forename: K
authors.initials: K
authors.lastname: Hansen