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<div><font face="Arial" size="+4" color="#000000">Seminar on<br>
</font><font face="Arial" size="+5" color="#000000"><b>Modern Optics
and Spectroscopy<br>
<br>
</b></font><font face="Arial" size="+4" color="#000000"><b>Mark
Johnson</b>, Yale University<br>
<br>
<i><b>Water at work: Using clusters to understand fundamental
aspects of aqueous chemistry<br>
<br>
</b></i></font><font face="Arial" size="+5" color="#000000">March 8,
2005<br>
12:00 - 1:00 p.m.<br>
<br>
<br>
<br>
</font><font face="Arial" size="+3"
color="#000000">Abstract</font></div>
<div><font face="Arial" size="+2" color="#000000">The so-called,
hydrated electron” has proven to be a very difficult</font></div>
<div><font face="Arial" size="+2" color="#000000">species to
understand on a molecular level since its discovery in<br>
1962. In this talk, we will elucidate the local network<br>
rearrangements that occur when a water cluster attaches an extra<br>
electron. This structural information is obtained by monitoring
the<br>
vibrational spectra of size-selected clusters using a supersonic
jet<br>
ion source interfaced to a double-focusing, tandem time-of-flight<br>
photofragmentation mass spectrometer. A major advance in
this<br>
technique that enables definitive structural assignment for the<br>
network morphologies is the use of a very broadly tunable ir probe<br>
laser. Parametric conversion in AgGaSe2 crystals, combined with
more<br>
typical mid-ir generation using KTP and KTA crystals, provide
coverage<br>
from 600-4600 wavenumbers for action spectroscopy in the scope of
a<br>
table-top laser system. We capitalize on this capability to
explore<br>
the evolution of electron accommodation with increasing numbers of<br>
water molecules. A surprising aspect of this study is that we
find<br>
one water molecule to be largely responsible for trapping the<br>
electron, and this binding motif survives for clusters containing
at<br>
least up to 25 water molecules</font></div>
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