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Atomic Physics Seminars
Monday, April 30, 2001
Physics Building, Room 204
Note special time.
[Host: Bob Jones/Eric Wells]
"Photoelectron Diffraction Mapping: Molecules Illuminated from Within"
Much of our knowledge of the internal structure of matter results from
the scattering and diffraction of electrons or X-rays. In many cases, the
matter under investigation is in crystalline (or absorbate) form and can
therefore be easily oriented in the laboratory. However, there are
fundamental questions that may only be addressed through the direct study
of single atoms or molecules (i.e. gas phase). It is therefore important
that we seek methods which allow the detailed exploration of the
orientation dependence of otherwise randomly oriented systems. I will
discuss the use of a multiparticle coincidence technique to image the
diffraction of an electron wave whose source is a specific site in a free
molecule, i.e. core-level photoelectrons are used to illuminate the
molecule from within. By choosing photons (and therefore photoelectrons)
of appropriate energy, we can cause the photoelectron to resonate as it
emerges through the molecular potential. This results in a richly
structured electron diffraction pattern in the body-fixed frame of the
randomly oriented molecule in the gas phase, and ultimately provides a
unique "fingerprint" of the molecular potential.
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