Seminar on
Modern Optics and Spectroscopy

Hans Bechtel, MIT

Partner swapping: Another reason to pump and dump

November 21, 2006

12:00 noon - 1:00 p.m. Grier Room 34-401

Abstract:

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 « HNC, HCCH « CCH2, and NCCN « 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.

TUESDAYS, 12:00-1:00, GRIER ROOM (34-401)
Refreshments served following the seminar

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