PHYS 618 |
| The aqueous hydroxyl radical is a critically important oxidizing species in atmospheric chemistry, industrial advanced oxidation processes, and nuclear reactor cooling loops. It has long been known that aqueous OH radicals absorb most strongly near 230nm rather than near 310nm as in the gas phase, and this “shift” has gone unexplained. We recently studied the UV spectrum of the hydroxyl radical between 230 and 320 nm in high temperature water using pulse radiolysis. It was found that the 230nm band attenuates at elevated temperature while a band grows in at 310 nm. The former was assigned to a transition involving hydrogen-bonded OH radicals, while the latter was attributed to “free” OH radicals. High level ab initio calculations on water-OH complexes have now allowed us to assign the 230nm absorbance to charge transfer from water to OH radicals in unusual hydrogen bonding arrangements. We are currently extending the spectral window of this work deeper into the UV and further into the visible to determine the temperature dependence of the long-wavelength absorption tail. These results will be discussed with reference to theoretical models of the OH radical absorption. |
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PHYS Poster Session - Computational Spectroscopy and Reaction Dynamics
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |