X-ray induced ultrafast charge transfer in thiophene-based conjugated polymers controlled by core-hole clock spectroscopy.

We explore ultrafast charge transfer (CT) resonantly induced by hard X-ray radiation in organic thiophene-based polymers at the sulfur K-edge. A combination of core-hole clock spectroscopy with real-time propagation time-dependent density functional theory simulations gives an insight into the electron dynamics underlying the CT process. Our method provides control over CT by a selective excitation of a specific resonance in the sulfur atom with monochromatic X-ray radiation.

Auger Shake-Up Assisted Electron Recapture.

The presence of doubly excited states (DESs) above the core-hole ionization threshold nontrivially modulates the x-ray absorption because the participator Auger decay couples DESs to the underlying low-energy core-hole continuum. We show that coupling also affects the high-energy continuum populated by the spectator Auger decay of DESs. For the K-L_{23}^{2} Auger decay of the 1s^{-1}3p^{-1}4s^{2}^{1}P state in argon, the competing nonresonant path is assigned to the recapture of the 1s photoelectron caused by emission of the fast electron from the shake-up K-L_{23}^{2} decay of the 1s^{-1} ion.

First (e,e) coincidence measurements on solvated sodium benzoate in water using a magnetic bottle time-of-flight spectrometer.

Understanding the mechanisms of X-ray radiation damage in biological systems is of prime interest in medicine (radioprotection, X-ray therapy…). Study of low-energy rays, such as soft-X rays and light ions, points to attribute their lethal effect to clusters of energy deposition by low-energy electrons. The first step, at the atomic or molecular level, is often the ionization of inner-shell electrons followed by Auger decay in an aqueous environment.

Concerted and sequential three-body fragmentation of deep-core-ionized carbon disulfide.

Momentum vector correlation is a powerful tool to study molecular dissociation. We have studied the three-body fragmentation of carbon disulfide after sulfur 1s photoionization by means of momentum imaging techniques. Concerted and sequential pathways are disentangled in three-body fragmentation using adapted analysis strategies.

Photochemical Ring-Opening Reaction of 1,3-Cyclohexadiene: Identifying the True Reactive State.

The photochemically induced ring-opening isomerization reaction of 1,3-cyclohexadiene to 1,3,5-hexatriene is a textbook example of a pericyclic reaction and has been amply investigated with advanced spectroscopic techniques. The main open question has been the identification of the single reactive state which drives the process. The generally accepted description of the isomerization pathway starts with a valence excitation to the lowest lying bright state, followed by a passage through a conical intersection to the lowest lying doubly excited state, and finally a branching between either the return to the ground state of the cyclic molecule or the actual ring-opening reaction leading to the open-chain isomer.