Time-resolved Stark effect in rapidly varying fields

The cycle-averaged ac Stark effect associated with the A²Σ⁺v′ = 2 ← X²Π_1/2v′ = 0 two-photon absorption of NO at intensities between 7.7 and 15.2 TWcm^-2 has been characterized in real time through a synergic combination of bichromatic laser experiments and quantum-dynamics calculations. Measurements of the fluorescence emitted by the Rydberg A²Σ⁺v′ = 2 level as a function of time between Stark and probe components of a bichromatic field exhibit a characteristic evolution in temporal peak structure with Stark-field intensity, which is interpreted in terms of a time-dependent Floquet analysis of the laser-matter interaction. The experimental observations are consistent with a dynamic Stark shift of Δε_s(ω₁, ω₂) ≤ 0.23 eV of the optical transition at these intensities.