Resonantly enhanced second-harmonic generation in atomic hydrogen was investigated near 121.6 nm. With the application of a dc electric field, it is shown that coupling of the 2s and 2p states produces resonantly enhanced nonlinear susceptibility and reduced absorption at the second-harmonic wavelength, resulting in an increased net efficiency of the second-harmonic-generation process.

• Received 28 August 1991

DOI:https://doi.org/10.1103/PhysRevA.45.5152