First laser-controlled antihydrogen production.

Lasers are used for the first time to control the production of antihydrogen (H ). Sequential, resonant charge exchange collisions are involved in a method that is very different than the only other method used so far-producing slow H during positron cooling of antiprotons in a nested Penning trap. Two attractive features are that the laser frequencies determine the H binding energy, and that the production of extremely cold H should be possible in principle-likely close to what is needed for confinement in a trap, as needed for precise laser spectroscopy.