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Atomic Physics Seminars

ics Atomic
Monday, April 30, 2001
4:00 PM
Physics Building, Room 204
Note special time.
Allen Landers [Host: Bob Jones/Eric Wells]
Western Michigan
"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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