Tsarev M, Ryabov A, Baum P
Universität Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany.
Phys Rev Lett. 2021 Oct 15;127(16):165501. doi: 10.1103/PhysRevLett.127.165501.
The temporal properties of an electron beam are decisive for modern ultrafast electron microscopy and for the quantum optics of the free electron in laser fields. Here, we report a time-domain interferometer that measures and distinguishes the pure and ensemble coherences of a free-electron beam in a transmission electron microscope via symmetry-breaking shifts of photon-order sideband peaks. This result is a free-electron analog to the reconstruction of attosecond busts and photoemission delays in optical attosecond spectroscopy. We find a substantial pure electron coherence that is connected to the thermodynamics of the emitter material and a lower ensemble coherence that is governed by space-charge effects. Pure temporal coherences above 5 fs are measured at >10^{9} electrons per second in a high-brightness beam.
电子束的时间特性对于现代超快电子显微镜以及激光场中自由电子的量子光学而言具有决定性意义。在此，我们报告了一种时域干涉仪，它通过光子阶边带峰的对称破缺位移来测量和区分透射电子显微镜中自由电子束的纯相干性和系综相干性。这一结果类似于光学阿秒光谱中阿秒脉冲串的重建和光发射延迟，是自由电子的一种类似情况。我们发现存在与发射体材料的热力学相关的显著纯电子相干性以及受空间电荷效应支配的较低系综相干性。在高亮度束流中，每秒超过(10^{9})个电子的情况下，测量到了高于(5)飞秒的纯时间相干性。
