Ultrafast X-Ray Molecular Dynamics

Transient absorption in the extreme ultraviolet and x-ray spectral regimes is used to probe chemical dynamics on both the femtosecond and attosecond timescales. Laser-produced high-order harmonics in the soft x-ray can investigate dissociating molecules, ring opening, passage through conical intersections, singlet to triplet transitions, and electronic and vibrational coherences. By extending the probe photon energies to 300 eV in the soft x-ray, carbon species are now readily investigated to reveal atom-specific electronic orbitals during electronic transformations of molecules. Product branches are observed directly and time measurements are obtained for the production of various excited state species. Transient features, indicative of x-ray spectroscopic transitions to dissociative or intermediate states are characterized. On ultrashort timescales, electronic and vibrational wave packet dynamics are observed. A remarkable time-resolved x-ray spectroscopic revolution provides novel opportunities for molecular dynamics investigations on femtosecond and attosecond timescales.