Photoelectron Spectroscopy of Cold Hydrated Sulfate Clusters, SO42−(H2O)n (n = 4−7): Temperature-Dependent Isomer Populations
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- 作者：Xue-Bin Wang ; Alina P. Sergeeva ; Jie Yang ; Xiao-Peng Xing ; Alexander I. Boldyrev ; Lai-Sheng Wang
- 刊名：Journal of Physical Chemistry A
- 出版年：2009
- 出版时间：May 14, 2009
- 年：2009
- 卷：113
- 期：19
- 页码：5567-5576
- 全文大小：496K
- 年卷期：v.113,no.19(May 14, 2009)
- ISSN：1520-5215
文摘
Sulfate is an important inorganic anion and its interactions with water are essential to understand its chemistry in aqueous solution. Studies of sulfate with well-controlled solvent numbers provide molecular-level information about the solute−solvent interactions and critical data to test theoretical methods for weakly bounded species. Here we report a low-temperature photoelectron spectroscopy study of hydrated sulfate clusters SO42−(H2O)n (n = 4−7) at 12 K and ab initio studies to understand the structures and dynamics of these unique solvated systems. A significant increase of electron binding energies was observed for the 12 K spectra relative to those at room temperature, suggesting different structural isomers were populated as a function of temperature. Theoretical calculations revealed a competition between isomers with optimal water−solute and water−water interactions. The global minimum isomers all possess higher electron binding energies due to their optimal water-solute interactions, giving rise to the binding energy shift in the 12 K spectra, whereas many additional low-lying isomers with less optimal solvent−solute interactions were populated at room temperature, resulting in a shift to lower electron binding energies in the observed spectra. The current work demonstrates and confirms the complexity of the water-sulfate potential energy landscape and the importance of temperature control in studying the solvent−solute systems and in comparing calculations with experiment.