Eric A. Hessels Ph.D. (Notre Dame) Distinguished Research Professor of Physics This e-mail address is being protected from spambots. You need JavaScript enabled to view it Research Field: Atomic, Molecular & Optical Physics Research specialization: Experimental atomic physics; High-precision measurements in excited states of few-electron atoms. Publications

Antihydrogen

A new idea for producing cold (trapable) antihydrogen is being developed in collaboration with Gerald Gabrielse at Harvard. The idea is to produce antihydrogen using two charge exchanges. For the first, a highly-excited cesium atom passes by a positron trapped in a Penning trap and as it passes, the positron can capture the loosely-bound electron from the cesium atom. This produces a highly-excited positronium atom. In the second charge exchange, this highly-excited positronium atom passes by an antiproton which is trapped in a nearby Penning trap, and this time the antiproton can capture the electron from the positronium atom, resulting in an antihydrogen atom. This work is being done in conjunction with the international ATRAP collaboration. The goal of this collaboration is to hold the antihydrogen atoms in a magnetic trap and to perform precision spectroscopy on them which will allow for very precise tests of the symmetries and physics of antimatter.

Fine-Structure Constant

We are making a precision measurement of the n=2 triplet P energy levels of atomic helium. The 2.3-GHz J=1-to-J=2 interval has been measured to an accuracy of 1.3 kHz and provides a stringent test of Quantum Electrodynamics in this simple two-electron atom. The 29.6-GHz J=0-to-J=1 interval is measured to an accuracy of 0.9 kHz, which makes possible a new 17-part-per-billion determination of the fine-structure constant. We are now working on new measurements with even higher precision and when these are completed and compared to theoretical predictions of similar accuracy, they will lead to a 3-part-per-billion determination of the constant.