New perspectives in time-resolved laser-induced electron diffraction

Abstract

Imaging the microscopic world in real space and real-time is a grand challenge of science. In the landscape of time-resolved imaging techniques, laser-induced electron diffraction (LIED) has recently shown to be a promising candidate to push the frontiers of ultrafast molecular imaging. In this work, we review the main achievements of LIED research in terms of experimental results and advanced modeling. We also envision interesting perspectives toward the future advancement of time-resolved LIED imaging.

Eliminating Artificial Boundary Conditions in Time-Dependent Density Functional Theory Using Fourier Contour Deformation

“…Similarly, by analyzing the “spider-leg” features formed by interference between direct and rescattered electrons, one can recover information on the time between rescattering events . A proper understanding of the details of the PAD, especially for large and complex molecules, is an active and significant area of research. − …”

Unraveling the ultrafast dynamics of thermal-energy chemical reactions

“…Laser-induced electron diffraction (LIED) is a very promising table-top-laser-based, sensitive technique 42,[145][146][147] for the imaging of ultrafast thermal-energy dynamics. LIED is an extension of PEMD to the rescattering regime, as sketched in Fig.…”

“…42,44,46,47,150 As the electron typically returns within a single cycle of the ionizing laser, the technique has the potential to image molecular structure on the few-femtosecond timescale 42 or even electronic dynamics. 43,147 However, while LIED is, in principle, single-molecule sensitive, the signal of the backscattered electrons is significantly weaker, by several orders of magnitude, compared to the socalled ''direct'' electrons. 151 This leads to experiments needing typically 10 4 -10 8 laser pulses to produce a single diffraction pattern, 44,145,152 i.e., a data collection time between B10 s and B1 day using a 1 kHz laser.…”

“…42,44,46,47,150 As the electron typically returns within a single cycle of the ionizing laser, the technique has the potential to image molecular structure on the few-femtosecond timescale 42 or even electronic dynamics. 43,147…”

“…Moreover, the application of LIED to pump-probe ''femtochemistry'' 2 experiments is hindered by the strongly varying ionization energies while the system traverses different electronic states. 147 With thermal-energy dynamics, one can expect small changes in the ionization energy of the system of interest, suggesting that the efficiency of the tunnel-ionization process, which is intrinsically linked to the Keldysh parameter, 154,155 will remain relatively constant. Conversely, as near-/mid-IR light is typically used to perform the strong-field ionization step, careful consideration of the wavelength used for LIED must be made to ensure that the probe does not inadvertently induce or alter the dynamics in the system itself.…”