Excitation, dynamics, and control of rotationally autoionizing Rydberg states of H2

Phys. Chem. Chem. Phys.

2017

Nonresonant inelastic electron and X-ray scattering cross sections for bound-to-bound transitions in atoms and molecules are calculated directly from ab initio electronic wavefunctions. The approach exploits analytical integrals of Gaussian-type functions over the scattering operator, which leads to accurate and efficient calculations. Ne atoms, open-shell C and Na atoms, and the N 2 molecule, with both inner-shell and valence electronic transitions considered. The method is appropriate for use in conjunction with quantum molecular dynamics simulations and for the analysis of new ultrafast X-ray scattering experiments.

Section: Discussionmentioning

confidence: 99%

Ab initio calculation of inelastic scattering

Carrascosa

Phys. Chem. Chem. Phys.

2017

“…It is straightforward to control the characteristic time scale of the dynamics by changing the excitation energy [21], and technologies exist to shape the wave packets [22,23]. The anisotropy induced by the optical excitation pulse increases the amount of information available.…”

mentioning

confidence: 99%

“…The expansion coefficients c i are determined by the response of the atoms to the pump pulse. In the absence of multiphoton processes, these coefficients are given by first order perturbation theory, with c i ¼ 2π{D is εðE is Þ, where εðEÞ is the spectral profile of the pump pulse and D is the state-specific dipole transition moment [21]. We now examine the structure of the wave packet in each atom in greater detail.…”

mentioning

confidence: 99%

How to Observe Coherent Electron Dynamics Directly

Suominen

2014

Phys. Rev. Lett.

Detection of electron motion by elastic scattering of short x-ray pulses from a coherent superposition of highly excited electronic states in rare gas atoms is investigated. The laser excitation of the electron wave packet introduces strong anisotropy which facilitates detection, and large differences in the radial distribution of the excited Rydberg and core electrons allow the dynamics to be detected using both soft and hard x rays.

“…One possible ansatz expands the wavepacket in the complete basis of orthonormal eigenstates |Ψ j of the molecular HamiltonianĤ 0 (see e.g., Ref. [36]),…”

Section: Wavepacket Dynamicsmentioning

confidence: 99%

Fundamental Limits on Spatial Resolution in Ultrafast X-ray Diffraction

Weber

2017

Applied Sciences

X-ray Free-Electron Lasers have made it possible to record time-sequences of diffraction images to determine changes in molecular geometry during ultrafast photochemical processes. Using state-of-the-art simulations in three molecules (deuterium, ethylene, and 1,3-cyclohexadiene), we demonstrate that the nature of the nuclear wavepacket initially prepared by the pump laser, and its subsequent dispersion as it propagates along the reaction path, limits the spatial resolution attainable in a structural dynamics experiment. The delocalization of the wavepacket leads to a pronounced damping of the diffraction signal at large values of the momentum transfer vector q, an observation supported by a simple analytical model. This suggests that high-q measurements, beyond 10-15 Å −1 , provide scant experimental payback, and that it may be advantageous to prioritize the signal-to-noise ratio and the time-resolution of the experiment as determined by parameters such as the repetition-rate, the photon flux, and the pulse durations. We expect these considerations to influence future experimental designs, including source development and detection schemes.