Characterizing multiphoton excitation using time-resolved X-ray scattering

TL;DR

This study uses time-resolved X-ray scattering to analyze multiphoton excitation in molecular iodine, enabling detailed mode-specific motion and dissociation dynamics measurement after laser excitation.

Contribution

It introduces a method combining temporal Fourier transform with X-ray scattering to distinguish and quantify different molecular motions and dissociation processes.

Findings

Mode-specific nuclear oscillations are accurately measured.

Dissociation velocities and timing are identified.

Laser-induced couplings among molecular potentials are revealed.

Abstract

Molecular iodine was photoexcited by a strong 800 nm laser, driving several channels of multiphoton excitation. The motion following photoexcitation was probed using time-resolved X-ray scattering, which produces a scattering map $S(Q,\tau)$. Temporal Fourier transform methods were employed to obtain a frequency-resolved X-ray scattering signal $\tilde{S}(Q,\omega)$. Taken together, $S(Q,\tau)$ and $\tilde{S}(Q,\omega)$ separate different modes of motion, so that mode-specific nuclear oscillatory positions, oscillation amplitudes, directions of motions, 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.