Attosecond chronoscopy has revealed small but measurable delays in photoionization, characterized by the ejection of an electron on absorption of a single photon. Ionization-delay measurements in atomic targets provide a wealth of information about the timing of the photoelectric effect, resonances, electron correlations and transport. However, extending this approach to molecules presents challenges, such as identifying the correct ionization channels and the effect of the anisotropic molecular landscape on the measured delays. Here, we measure ionization delays from ethyl iodide around a giant dipole resonance. By using the theoretical value for the iodine atom as a reference, we disentangle the contribution from the functional ethyl group, which is responsible for the characteristic chemical reactivity of a molecule. We find a substantial additional delay caused by the presence of a functional group, which encodes the effect of the molecular potential on the departing electron. Such information is inaccessible to the conventional approach of measuring photoionization cross-sections. The results establish ionization-delay measurements as a valuable tool in investigating the electronic properties of molecules.

阿秒秒表已显示出光电离中的微小但可测量的延迟，其特征在于吸收单个光子时会弹出电子。原子靶中的电离延迟测量提供了大量有关光电效应，共振，电子相关性和传输的时间信息。但是，将这种方法扩展到分子会带来挑战，例如，确定正确的电离通道以及各向异性分子景观对所测延迟的影响。在这里，我们测量围绕巨大偶极子共振的乙基碘的电离延迟。通过使用碘原子的理论值作为参考，我们可以解开功能乙基的贡献，该功能乙基负责分子的特征化学反应性。我们发现由于官能团的存在而引起的大量额外延迟，该官能团编码分子势对离去的电子的影响。这种信息是常规的测量光电离截面的方法所无法获得的。结果建立了电离延迟测量，这是研究分子电子特性的宝贵工具。