[MOS] MOS March 8

[Zina Queen]

Seminar on
Modern Optics and Spectroscopy

Mark Johnson, Yale University

Water at work:  Using clusters to understand 
fundamental aspects of aqueous chemistry

March 8, 2005
12:00 - 1:00 p.m.



Abstract
The so-called, hydrated electron” has proven to be a very difficult
species to understand on a molecular level since its discovery in
1962.  In this talk, we will elucidate the local network
rearrangements that occur when a water cluster attaches an extra
electron.  This structural information is obtained by monitoring the
vibrational spectra of size-selected clusters using a supersonic jet
ion source interfaced to a double-focusing, tandem time-of-flight
photofragmentation mass spectrometer.  A major advance in this
technique that enables definitive structural assignment for the
network morphologies is the use of a very broadly tunable ir probe
laser.  Parametric conversion in AgGaSe2 crystals, combined with more
typical mid-ir generation using KTP and KTA crystals, provide coverage
from 600-4600 wavenumbers for action spectroscopy in the scope of a
table-top laser system.  We capitalize on this capability to explore
the evolution of electron accommodation with increasing numbers of
water molecules.  A surprising aspect of this study is that we find
one water molecule to be largely responsible for trapping the
electron, and this binding motif survives for clusters containing at
least up to 25 water molecules
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.mit.edu/pipermail/mos/attachments/20050304/810be605/attachment.htm