22.06.2015 X-ray pulses from the Linac Coherent Light Source probe the molecular dynamics of photoexcitation. X-rays from the Linac Coher...
Ultrafast X-ray Auger probing of photoexcited molecular dynamics.
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Nature communications, ISSN: 2041-1723, Vol: 5, Issue: 1, Page: 4235
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- Chemistry; Biochemistry, Genetics and Molecular Biology; Physics and Astronomy; RESOLVED PHOTOELECTRON-SPECTROSCOPY; FREE-ELECTRON LASER; CONICAL INTERSECTIONS; EXCITED-STATES; RNA BASES; AQUEOUS-SOLUTION; THYMINE; DNA; OPERATION; URACIL
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Molecules can efficiently and selectively convert light energy into other degrees of freedom. Disentangling the underlying ultrafast motion of electrons and nuclei of the photoexcited molecule presents a challenge to current spectroscopic approaches. Here we explore the photoexcited dynamics of molecules by an interaction with an ultrafast X-ray pulse creating a highly localized core hole that decays via Auger emission. We discover that the Auger spectrum as a function of photoexcitation--X-ray-probe delay contains valuable information about the nuclear and electronic degrees of freedom from an element-specific point of view. For the nucleobase thymine, the oxygen Auger spectrum shifts towards high kinetic energies, resulting from a particular C-O bond stretch in the ππ* photoexcited state. A subsequent shift of the Auger spectrum towards lower kinetic energies displays the electronic relaxation of the initial photoexcited state within 200 fs. Ab-initio simulations reinforce our interpretation and indicate an electronic decay to the nπ* state.