Heat capacities of freely evaporating charged water clusters
Artikel i vetenskaplig tidskrift, 2009

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 $N=5$ to $300$. 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 6-8 $k_B$ 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 $^o$C values.

water clusters

thermodynamics properties


Erika Sundén

Göteborgs universitet

K Stöchkel

Aarhus Universitet

S Panja

Aarhus Universitet

U Kadhane

Aarhus Universitet

P. Hvelplund

Aarhus Universitet

S. Brøndsted Nielsen

Aarhus Universitet

H. Zettergren

Aarhus Universitet

Bertil Dynefors

Chalmers, Teknisk fysik

Klavs Hansen

Göteborgs universitet

Journal of Chemical Physics

0021-9606 (ISSN) 1089-7690 (eISSN)

Vol. 130 224308-


Atom- och molekylfysik och optik