The first observation of laser-induced recombination, performed with merged beams of protons, electrons, and laser photons in an ion storage ring, is reported. The process was used to study the photorecombination spectrum with high resolution. Deviations from earlier theoretical predictions turned out to be due to a weak external electric field and could be well described by a simple extension of the field-free quantum-mechanical theory, based on properties of the classical electron trajectories in the combined external and Coulomb fields.

• Received 28 February 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.22