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<div><font face="Arial" size="+2" color="#000000">Seminar on<br>
<b>Modern Optics and Spectroscopy<br>
<br>
Tim Zwier</b>, Purdue University<br>
<br>
<i><b>Single conformation vibrational spectroscopy and isomerization
dynamics<br>
<br>
</b></i>March 29, 2005<br>
12:00 - 1:00 p.m.</font></div>
<div><font face="Arial" size="+2" color="#000000">Grier Room
34-401<br>
<br>
<br>
Abstract<br>
<br>
<br>
Conformational isomerization is an important class of unimolecular
reaction which encompasses situations ranging from simple<i>
cis-trans</i> isomerization in a double minimum potential well to the
staggering complexity associated with the potential energy landscape
for protein folding. In studies of conformational isomers, the
field of molecular spectroscopy has traditionally focused attention on
the minima on the potential energy surface, since this is where the
bulk of the population resides. However, if one is interested in
understanding the kinetics or dynamics of such processes, it is the
barriers to isomerization that are of primary importance. In
this talk, I will describe recent results from our group using
population transfer spectroscopy, a laser based pump-probe method that
measures the energetic thresholds for isomerization between specific
X_Y reactant-product pairs. From a series of such measurements,
it is possible to map out the relative energies of the key stationary
points (both minima and transition states) on the potential energy
surface. Among the examples to be discussed are studies of
conformational isomerization in isolated flexible biomolecules and
water-containing complexes, including cases in which the isomerization
involves motion of a single solvent molecule between hydrogen bonding
sites on a solute.</font></div>
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