Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
X-ray Transient Absorption Spectroscopy (XTAS) and theoretical calculations are used to study CCl 4 + prepared by 800 nm strong-field ionization. XTAS simultaneously probes atoms at the carbon K-edge (280–300 eV) and chlorine L-edge (195–220 eV). Comparison of experiment to X-ray spectra computed by orbital-optimized density functional theory (OO-DFT) indicates that after ionization, CCl 4 + undergoes symmetry breaking driven by Jahn–Teller distortion away from the initial tetrahedral structure (T d ) in 6 ± 2 fs. The resultant symmetry-broken covalently bonded form subsequently separates to a noncovalently bound complex between CCl 3 + and Cl over 90 ± 10 fs, which is again predicted by theory. Finally, after more than 800 fs, L-edge signals for atomic Cl are observed, indicating dissociation to free CCl 3 + and Cl. The results for Jahn–Teller distortion to the symmetry-broken form of CCl 4 + and formation of the Cl–CCl+3 complex characterize previously unobserved new species along the route to dissociation.more » « less
-
Berman, Michael R. ; Young, Linda ; Dai, Hai-Lung (Ed.)X-ray absorption spectroscopy on attosecond and femtosecond timescales is a frontier of modern ultrafast science. For the last two decades, ultrafast lasers produced ever growing powers that facilitate implementation of attosecond high-harmonic soft X-ray sources in compact equipment. This unique broad-band light source opens the door for numerous applications; in particular it is ideal for chemical dynamics studies due to its sensitivity to electronic and vibrational state changes. Here, we outline briefly the evolution of time-resolved technology and review several case studies in which extreme ultraviolet and soft X-ray spectroscopy prove its exclusive sensitivity to the electronic structure of molecular species.more » « less
-
Abstract Electronic relaxation in organic chromophores often proceeds via states not directly accessible by photoexcitation. We report on the photoinduced dynamics of pyrazine that involves such states, excited by a 267 nm laser and probed with X-ray transient absorption spectroscopy in a table-top setup. In addition to the previously characterized1B2u(ππ*) (S2) and1B3u(nπ*) (S1) states, the participation of the optically dark1Au(nπ*) state is assigned by a combination of experimental X-ray core-to-valence spectroscopy, electronic structure calculations, nonadiabatic dynamics simulations, and X-ray spectral computations. Despite1Au(nπ*) and1B3u(nπ*) states having similar energies at relaxed geometry, their X-ray absorption spectra differ largely in transition energy and oscillator strength. The1Au(nπ*) state is populated in 200 ± 50 femtoseconds after electronic excitation and plays a key role in the relaxation of pyrazine to the ground state.