Linear Stark Effect Due to Resonant Interactions of Static and Dynamic Fields

We investigated the line shape of the Lyman-$\alpha$ transition of a hydrogen atom simultaneously subjected to a static and a perpendicular high-frequency electric field. It was found that resonance effects occur, producing a profile substantially different from the Stark spectrum of the fields acting independently. This result shows that the interpretation of turbulent hydrogen plasma spectra by the Blokhintsev (dynamic field only) theory is not generally valid.