High-harmonic-driven inverse Raman scattering

Spectral analysis of high-order harmonics generated by ultrashort mid-infrared pulses in molecular nitrogen reveals well-resolved signatures of inverse Raman scattering, showing up near the frequencies of prominent vibrational transitions of nitrogen molecules. When tuned on a resonance with the v ′ = 0 → v ′ ′ = 0 pathway within the B 3 Π g → C 3 Π u second positive system of molecular nitrogen, the eleventh harmonic of a 3.9 µm, 80 fs driver is shown to acquire a distinctive antisymmetric spectral profile with red-shifted bright and blue-shifted dark features as indicators of stimulated Raman gain and loss. This high-harmonic setting extends the inverse Raman effect to a vast class of strong-field light–matter interaction scenarios.