Site-Specific Generation of Excited State Wavepackets with High-Intensity Attosecond X-rays

Non-linear interactions with strong-field, ultrafast x-rays, made possible by recent XFEL developments, can produce coherent superpositions of valence excited states. This offers the potential to observe charge migration dynamics prior to excited state nuclear motion. The broad-band, high-field nature of the required pulses results in a multitude of accessible excited states of both valence and Rydberg nature.  This work uses multiconfigurational quantum chemistry in conjunction with the time-dependent Schrödinger equation to evaluate the population transfer dynamics in impulsive stimulated x-ray Raman scattering on nitric oxide, following the recent experimental and theoretical advances at the oxygen K-edge [1].  A comparative assessment is made between the oxygen and nitrogen K-edges, using chemical insights gained from the resonant inelastic x-ray scattering [2].  Effects from the electronic structure calculations and pulse conditions on the population transfer are explored, highlighting complexities attributed to the Rabi frequency. High state-selectivity for Rydberg-valence excited states is achieved via an orthogonally polarized two-color stimulated-RIXS setup.

[1] O’Neal, J. T.; et. al. Phys. Rev. Lett. 2020, 125, 073203 

[2] Fouda, A. E. A.; et. al. J. Phys. Chem. Lett. 2020, 11, 18, 7476–7482c