Photon-Stimulated Desorption of Cations from Ionic Solutions
EMSL Project ID
9099
Abstract
The most basic task in understanding heterogeneous reactions is to understand the states of the reactants that take part in the proposed reactions. Ionized or solvated species (Cl-) will behave much differently than molecular NaCl. Previous studies of cation desorption from low temperature (80 -140 K) pristine water ice surfaces show a temperature dependence which can be explained in terms of the electronic structure, local bonding geometry, excited state lifetimes and hole hopping ability in the terminal water molecules. Low doses of HCl on low-temperature water ice affect the cation desorption yield by occupying dangling bonds and causing distortions in the bond lengths of the surrounding water molecules. The solvation of the HCl induces changes in the local crystalline structure of the ice surrounding the ionized species as the molecules reorient to solvate the ions. This reorientation changes the excited state lifetimes reflected by the change in the cation desorption yields. The change in the cation desorption yield provides a sensitive technique to probe the terminal water molecules.
We intend to investigate the surface states of ionic solutions through the photon-stimulated desorption (PSD) and time-of-flight reflectron mass spectrometry. The liquid jet will allow us to probe ionic solutions at temperatures above those viable with our current UHV system. The continuum of temperatures will provide a complete picture of the atmospherically relevant ionic interfaces.
The proposed research includes a detailed study of the threshold energy for cation desorption from a number of ionic liquids (NaCl, KCl, NaBr). Several ionic solutions will be studied to determine the effect of the cation and anion. The dependence of the cation yield on the photon energy, concentration of ions, and temperature will also be determined. A complete examination of the PSD of ionic solutions will give us insight into the electronic structure and local geometry of this atmospherically relevant surface.
Project Details
Project type
Exploratory Research
Start Date
2006-02-06
End Date
2005-05-31
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Grieves GA, NG Petrik, J Herring-Captain, B Olanrewaju, A Aleksandrov, RG Tonkyn, SE Barlow, GA Kimmel, and TM Orlando. 2008. "Photoionization of Sodium Salt Solutions in a Liquid Jet." Journal of Physical Chemistry C 112(22):8359-8364. doi:10.1021/jp7102534