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Heat capacities of freely evaporating charged water clusters
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View: Figures


Image of FIG. 1.
FIG. 1.

The experimental setup. Clusters are produced in a corona discharge in ambient air and enter the chamber through the capillary. The inset shows a magnified view of the corona discharge source, turned clockwise. The large figure shows the entire apparatus with the free flight distance at 3.4 m indicated. The ’s in the figure are explained in the text.

Image of FIG. 2.
FIG. 2.

Cluster size distribution of obtained by scanning the field in the magnet. The maximum intensity for the distributions shifts toward larger cluster sizes with decreasing temperature of the capillary. The scans at , 30, and where terminated at the masses indicated by the vertical bars. Individual mass peaks have been integrated and the spectra normalized to the highest intensity in each spectrum. The ion intensity variations are related to the stability of specific clusters and not caused by poor statistics.

Image of FIG. 3.
FIG. 3.

Evaporation spectra of the parent cluster in (a) and in (b). The peaks showing loss of multiple molecules in (a) are used to correct for CID. The inset here and in Fig. 4 is a semilogarithmic plot of the data.

Image of FIG. 4.
FIG. 4.

Evaporation spectra of the parent cluster in (a) and in (b). is most likely for and for .

Image of FIG. 5.
FIG. 5.

Normalized abundances after free flight where the symbols represent undissociated parent clusters (×), singly dissociated (○), doubly dissociated , and triply dissociated clusters (◇).

Image of FIG. 6.
FIG. 6.

Example of integrated and corrected abundances (○) and the fit using the Poisson distribution for both positive and negative clusters with and 225.

Image of FIG. 7.
FIG. 7.

Test of the approximation to use (the surviving fractions of the parent clusters) to represent the distribution of average number of water molecules lost. The ’s obtained by using either the whole evaporation spectrum (×) or calculated as (○).

Image of FIG. 8.
FIG. 8.

A schematic drawing of the energy distribution of the small cluster ensemble. The clusters are depleted from the high energy side of the energy distribution. The times refer to the different times of passage in the apparatus.

Image of FIG. 9.
FIG. 9.

The dimensionless heat capacities for positively (○) and negatively charged clusters (×). The lines are given for reference and represent literature values for bulk ice [at atm and (topmost ice line), (middle line), and (bottom line, from Ref. 19) and for bulk liquid water (at atm and , 50, and , from Ref. 20). The liquid water lines almost coincide.

Image of FIG. 10.
FIG. 10.

The temperature calculated using dissociation energies from the liquid drop model and the relation . The solid line includes the cohesive energy, surface tension, and charge energy. The dotted line represents the calculated when the charge effect is neglected. Sizes down to are plotted. The inset shows the dissociation energy used for the calculation, with and without the charging energy included.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Heat capacities of freely evaporating charged water clusters