Sub‐10‐fs Timing for Ultrafast Electron Diffraction with THz‐Driven Streak Camera

Abstract

Ultrafast electron diffraction (UED) has evolved to be a powerful tool for the study of structural dynamics with subpicosecond temporal resolution and subatomic spatial resolution. Recently, there have been intense research efforts toward femtosecond timing jitter and stability for improving the temporal resolution of UEDs, however, so far there has been no work showing long‐term (e.g., >1 h) stable timing for MeV‐level UED systems. In this article, a comprehensive timing synchronization method, based on optical‐radiofrequency synchronization and THz streaking, is demonstrated to maintain sub‐10‐fs long‐term timing stability for radiofrequency‐gun‐based MeV‐level UED, which results in 5.5 fs root‐mean‐square timing drift maintained over 4600 s. With high electron energy and low timing drift, the demonstrated capability is an important step toward studying ultrafast phenomena in samples with low scattering power, such as volatile gases and 2D materials.

Imaging Purely Nuclear Quantum Dynamics in Molecules by Combined X-ray and Electron Diffraction

“…Ultrafast X-ray and electron diffraction are complementary techniques for monitoring transient molecular structures. Comparisons of the two techniques have been discussed extensively. ,,, Even though X-ray diffraction has a much smaller cross section and covers a smaller regime of scattering angles, the high flux and energy of free electron laser X-ray pulses make up for these shortcomings. , The relativistic megaelectron volt electron pulses , with advanced time-sorting methods , largely overcome the space-charge effects, making femtosecond-resolved electron diffraction signals comparable to X-ray diffraction. We have simulated diffraction signals over a broad range of scattering vectors ( q up to 30 Å –1 ).…”

785-nm Frequency Comb-Based Time-of-Flight Detection for 3D Surface Profilometry of Silicon Devices

“…In order to generate the frequency-locked electronic signal as well as to detect the TOF changes, two EOS-TDs are employed. Among several EOS-TD configurations [25]- [28], we used the all-PM-fiber Sagnac-loop interferometer configuration, which was also previously employed for long-term sub-10-fs synchronization between an 800-nm Ti:sapphire laser and a microwave oscillator for ultrafast electron diffraction (UED) facilities [29]- [31]. The reference arm and the EOS-TD 1 (in Fig.…”

Ultrafast Imaging of Molecular Dynamics Using Ultrafast Low-Frequency Lasers, X-ray Free Electron Lasers, and Electron Pulses

“…The spatial charge broadening due to Coulomb repulsion of electrons and group velocity mismatch between electron and laser pulses decreases the temporal resolution, which can be remedied by relativistic electron acceleration or electron bunch compression. , Because the longitudinal space-charge pulse elongation is proportional to 1/β 2 γ 5 , where β = v / c , γ = (1−β 2 ) −1/2 , and v and c are the speed of electrons and vacuum light speed, respectively, the spatial charge effect can be greatly diminished for relativistic electrons. , MeV electron diffraction based on an S -band photocathode rf gun pulse compression can achieve 100 fs temporal resolution of polycrystalline diffraction aluminum foil and 65 fs temporal resolution for gas-phase diffraction of CF 3 I, which significantly improved the application of gas-phase and crystalline MeV ultrafast electron diffraction. The prospect of reaching 10 fs temporal resolution by relativistic electron sources , has great potential for the exciting development of mapping atomic motions and molecular dynamics.…”

“…43,112 MeV electron diffraction based on an S-band photocathode rf gun pulse compression can achieve 100 fs temporal resolution of polycrystalline diffraction aluminum foil 116 and 65 fs temporal resolution for gas-phase diffraction of CF 3 I, 117 which significantly improved the application of gas-phase and crystalline MeV ultrafast electron diffraction. The prospect of reaching 10 fs temporal resolution by relativistic electron sources 118,119 has great potential for the exciting development of mapping atomic motions and molecular dynamics.…”