Continuous Wave Coherent Lyman-a Radiation

The hydrogen atom is an important testing ground for fundamental theories. High resolution laser spectroscopy has provided cornerstones such as the measurement of fundamental constants, a test of quantum electrodynamics, and even the investigation of hadronic structure [1]. The recent production of antihydrogen atoms [2], albeit at almost the speed of light, has given prospect of a new field. Precise tests of the fundamental CPT symmetry [3] and even a comparison of the gravitational force on matter and antimatter [4] now challenge both experimental and theoretical physicists. Two experiments using the new Antiproton Decelerator (AD) at CERN [5] are now in preparation with the goal of precision measurements on magnetically trapped antihydrogen [6]. The narrow 1S-2S transition is an especially intriguing candidate for ultimate precision experiments. The excitation rate for this two-photon transition, however, is typically rather small. Previous experiments on ordinary hydrogen compensated that by the use of many atoms (1015 1017 atoms s in a beam [7,8], 101