Attosecond spectroscopy^{1,2,3,4,5,6,7} can resolve electronic processes directly in time, but a movie-like space–time recording is impeded by the too long wavelength (~100 times larger than atomic distances) or the source–sample entanglement in re-collision techniques^8,9,10,11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons^{1,2,3,4,5,6,7} or re-colliding wavepackets^8,9,10,11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a < 10-as delay of Bragg emission and demonstrates the possibility of analytic attosecond–ångström diffraction. Real-space electron microscopy visualizes with sub-light-cycle resolution how an optical wave propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space–time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

阿秒光谱法^{1,2,3,4,5,6,7}可以直接解决电子过程，但是像电影一样的时空记录会因波长太长（比原子距离大约100倍）而受阻。重新碰撞技术中的源-样本纠缠^8,9,10,11。在这里，我们通过使用自由空间电子代替高次谐波光子^{1,2,3,4,5,6,7}或重新碰撞波包^{8,9,10,11，将}阿秒计量学提高到皮秒波长和亚原子分辨率。de Broglie波长为4.5-pm的70keV电子束被激光周期的电场调制成具有亚光学周期持续时间的电子脉冲序列。晶体硅的时间分辨衍射揭示了小于10的布拉格发射延迟，并证明了分析阿秒-ngström衍射的可能性。现实空间电子显微镜以亚光周期分辨率可视化光波在空间和时间中的传播方式。电子显微镜和衍射技术结合了阿秒科学，可以对电子显微镜可以访问的整个样品形态范围内的光驱动过程进行时空成像。