Characterizing multiphoton excitation using time-resolved x-ray scattering*

Molecular iodine was photoexcited by a strong 800 nm laser, driving Raman excitation of vibrational states on the ground state as well as multiphoton dissociation. The subsequent motion following photoexcitation is observed using time-resolved x-ray scattering (TRXS) and analyzed using the temporal Fourier transform of TRXS, called frequency-resolved x-ray scattering (FRXS). The FRXS signal identifies vibrations with a beat frequency of 40.3$+$-1.0 THz oscillating about an equilibrium position of 0.28$+$-0.01nm, which match the expected beat frequency and equilibrium position for Raman excited vibrations on the ground state. Molecular dissociation also has a distinct signature in FRXS, which may be used to identify both velocities and initial positions of the dissociation channels.