Characterizing Multiphoton Excitation Using Time-Resolved X-ray Scattering

Abstract

Molecular iodine is photoexcited by a strong 800-nm laser driving several channels of multiphoton excitation. The motion following photoexcitation is probed using time-resolved x-ray scattering, which produces a scattering map S(Q,τ). Temporal Fourier-transform methods are employed to obtain a frequency-resolved x-ray-scattering signal S[over ˜](Q,ω). Taken together, S(Q,τ) and S[over ˜](Q,ω) separate different modes of motion so that mode-specific nuclear oscillatory positions, oscillation amplitudes, directions of motion, and times may be measured accurately. Molecular dissociations likewise have a distinct signature, which may be used to identify both velocities and dissociation time shifts and also can reveal laser-induced couplings among the molecular potentials.