Offentliggjort onsdag 27. januar 2010

Dato

fredag 26. februar 2010

Tid

06.30 - 08.00

Sted

Fysisk Auditorium

AMO PHYSICS SEMINAR

Speaker: R.D. DuBois, Missouri University of Science and Technology

Title: How Positrons Are Used To Understand the Physics and Properties of Matter

Time: Thursday, February 25, 15.15 to 16.00
Place: Fysisk Auditorium

Abstract:
The first antiparticle, the positron, was discovered over 70 years ago. Since then positrons have been used in many fields, ranging from medicine to chemistry to condensed matter and atomic physics studies. With respect to atomic physics, positron (and more recently, antiproton) based studies are providing very sensitive tests of theoretical models of atomic interactions and kinematics. For example, by comparing positron and electron impact data, specific interaction mechanisms can be isolated; changing the sign of the charge, e.g., the direction of the Coulomb force, alters the target polarization and the pre- and post-collision interactions. Experimentally, because antiparticle (positron or antiproton) beam intensities are extremely weak compared to those for electrons and ions, the vast majority of antiparticle-based studies to date have been restricted to total cross section measurements. We have developed techniques suitable for highly differential ionization studies using extremely weak beams and are now able to perform kinematically complete experiments for single ionization and doubly differential measurements for double ionization. Examples of these data plus a general overview of the various types of positron-based studies and techniques will be given.

Prof. Dubois would like to thank the Fulbright Commission for support for his visit to Aarhus University.

Peter Staanum and Nicolai Nygaard

Coffee, tea and fruit will be served at 15.05