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<div><font face="Arial" size="+1" color="#000000">Seminar on<br>
<b>Modern Optics and Spectroscopy<br>
<br>
<br>
Hans Bechtel</b>, MIT<br>
<br>
<i><b>Partner swapping: Another reason to pump and dump<br>
<br>
</b></i>November 21, 2006<br>
<br>
12:00 noon - 1:00 p.m.</font></div>
<div><font face="Arial" size="+1" color="#000000">Grier Room
34-401</font></div>
<div><font face="Arial" size="+1" color="#000000"><br>
<br>
<br>
<b>Abstract:<br>
<br>
</b></font><font face="Times New Roman" size="+1"
color="#000000">Isomerization reactions, in which a molecule keeps the
same set of atoms, but swaps partners, are prevalent in all areas of
chemistry and have strong implications for astronomy, biology,
combustion, and the environment. We study prototypical
isomerization reactions with high energy barriers such as
HCN</font><font face="Symbol" size="+1" color="#000000">
î</font><font face="Times New Roman" size="+1" color="#000000"> HNC,
HCCH</font><font face="Symbol" size="+1" color="#000000">
î</font><font face="Times New Roman" size="+1" color="#000000"> CCH2,
and NCCN</font><font face="Symbol" size="+1" color="#000000">
î</font><font face="Times New Roman" size="+1" color="#000000"> NCNC.
In order to better elucidate the nature of these reactions, we wish to
observe molecules in states of undress, i.e. near the top of the
energy barrier while old bonds are being broken and new bonds are
being formed. These barrier proximal states are hard to identify
because they are only a small subset of the more numerous and less
interesting highly excited vibrational states. The large
amplitude motion embodied in the rare barrier-proximal states,
however, causes changes in the electronic properties of the molecule
that provide markers to distinguish them from other states. To
prepare these highly energetic states with non-equilibrium motions, we
rely on stimulated emission pumping (SEP), a double resonance
technique involving a PUMP laser to an excited electronic state and a
DUMP laser back to the ground electronic potential energy
surface.</font></div>
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