Simultaneous observation of nuclear and electronic dynamics by ultrafast electron diffraction

Abstract

Simultaneous observation of nuclear and electronic motion is crucial for a complete understanding of molecular dynamics in excited electronic states. It is challenging for a single experiment to independently follow both electronic and nuclear dynamics at the same time. Here we show that ultrafast electron diffraction can be used to simultaneously record both electronic and nuclear dynamics in isolated pyridine molecules, naturally disentangling the two components. Electronic state changes (S1→S0 internal conversion) were reflected by a strong transient signal in small-angle inelastic scattering, and nuclear structural changes (ring puckering) were monitored by large-angle elastic diffraction. Supported by ab initio nonadiabatic molecular dynamics and diffraction simulations, our experiment provides a clear view of the interplay between electronic and nuclear dynamics of the photoexcited pyridine molecule.

Imaging conical intersection dynamics during azobenzene photoisomerization by ultrafast X-ray diffraction

“…Time-resolved diffraction movies can monitor the electronic charge density evolution during a chemical process (12)(13)(14)(15)(16)(17)(18)(19). A complementary technique is ultrafast electron diffraction, where the X-rays are replaced by bright electron pulses that scatter from the total (nuclear + electronic) charge density (20)(21)(22)(23)(24).…”

High-resolution movies of molecular rotational dynamics captured with ultrafast electron diffraction

“…The first application of MeV electron gun technology to gas-phase UED has resulted in a temporal resolution of 230 fs [17] and more recently 150 fs [18], compared to 850 fs for keV instruments [4]. This has enabled major scientific advances such as the observation of coherent rotation and vibrational motion [17,19]; capturing the passage of a nuclear wave packet through a conical intersection [18]; retrieving transient structures and observing structural dynamics in the electronic ground state [20]; resolving a ring opening reaction [21]; and, more recently, simultaneously capturing nuclear and electronic changes [22]. The main limitation of gas-phase MeV UED has been the low electron beam current, which results in low signal levels and long acquisition times.…”

Molecular structure retrieval directly from laboratory-frame photoelectron spectra in laser-induced electron diffraction

“…Similar SD-based iterative algorithms have also been used in field-free UED and conventional electron diffraction to accurately extract bond lengths within a small forward scattering angle (i.e. <10°) 12,14,15,26,27 . The Fourier-transform LIED (FT-LIED) 14,21,23 method, also called fixed-angle broadband laserdriven electron scattering (FABLES) 8 , retrieves the DCS in the backward scattering direction (i.e.…”