The quantum-mechanical motion of electrons in molecules and solids occurs on the sub-femtosecond timescale. Consequently, the study of ultrafast electronic phenomena requires the generation of laser pulses shorter than 1 fs and of sufficient intensity to interact with their target with high probability. Probing these dynamics with atomic-site specificity requires the extension of sub-femtosecond pulses to the soft X-ray spectral region. Here, we report the generation of isolated soft X-ray attosecond pulses with an X-ray free-electron laser. Our source has a pulse energy that is millions of times larger than any other source of isolated attosecond pulses in the soft X-ray spectral region, with a peak power exceeding 100 GW. This unique combination of high intensity, high photon energy and short pulse duration enables the investigation of electron dynamics with X-ray nonlinear spectroscopy and single-particle imaging, unlocking a path towards a new era of attosecond science.

电子在分子和固体中的量子力学运动发生在亚飞秒级的时标上。因此，对超快电子现象的研究要求产生短于1 fs的激光脉冲，并且具有足够的强度以高概率与其目标相互作用。用原子位点特异性探测这些动力学需要将亚飞秒脉冲扩展到软X射线光谱区域。在这里，我们报告了使用X射线自由电子激光器产生的孤立的软X射线阿秒脉冲的产生。我们的源的脉冲能量比软X射线光谱区域中任何其他孤立的阿秒脉冲源的脉冲能量都大数百万倍，峰值功率超过100 GW。高强度的独特结合，