Femtosecond gas phase electron diffraction with MeV electrons

摘要: We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in phase because pulses can probe structure high spatial resolution. Until recently, however, it was not possible for reach relevant timescale motion of nuclei during reaction. Using has allowed us overcome main challenges reaching resolution, namely delivering short target, overcoming effect velocity mismatch between pump laser and pulses, maintaining low timing jitter. At kinetic energies above 3 MeV, becomes negligible. The relativistic electrons are also less susceptible temporal broadening due Coulomb force. One that small de Broglie wavelength very angles. In this paper we describe new setup its characterization, including capturing static patterns molecules phase, finding time-zero sub-picosecond accuracy first time-resolved experiments. device achieve 100 fs root-mean-square, sub-angstrom collimation beam sufficient measure pattern, transverse coherence order 2 nm. Currently, limited both by pulse duration target jitter, while average current signal-to-noise ratio detection system. discuss plans improving