Modern ultrashort X-ray/XUV (extreme ultraviolet) sources provide unique opportunities to investigate the primary reactions of matter upon energetic excitation. Understanding these processes in molecules on ultrafast timescales is required to improve bespoke high-energy radiation detectors, nanomedicine schemes or to study the molecular composition of interstellar media. However, current experiments struggle to provide a general framework because of the uniqueness and complexity of each system. Here we show the universal role of correlation bands—features created by electron correlation. This is done by studying ultrafast energy relaxation of size-scalable two-dimensional molecules following ionization by an ultrashort XUV pulse. We observed long lifetimes that nonlinearly increase with the number of valence electrons. A general law based on solid-like electron–phonon scattering is proposed, which explains both our results and previously reported measurements. This offers new opportunities in attosecond science and high-energy photophysics.

现代超短波X射线/ XUV（极端紫外线）源为研究物质在高能激发下的主要反应提供了独特的机会。需要以超快的时间尺度了解分子中的这些过程，以改进定制的高能辐射探测器，纳米医学方案或研究星际介质的分子组成。但是，由于每个系统的独特性和复杂性，当前的实验难以提供一个通用的框架。在这里，我们展示了相关带的普遍作用-由电子相关创建的特征。这是通过研究超短XUV脉冲电离后可尺寸缩放的二维分子的超快能量弛豫来完成的。我们观察到长寿命随着价电子数量的增加而非线性增加。提出了基于固体电子-声子散射的一般定律，它解释了我们的结果和先前报道的测量结果。这为原子秒科学和高能光物理提供了新的机会。