近日，德国电子同步加速器DESY的Francesca Calegari&Vincent Wanie及其研究团队取得一项新进展。经过不懈努力，他们实现了紫外线激发分子中电子驱动手性动力学的捕获。相关研究成果已于2024年5月22日在国际权威学术期刊《自然》上发表。

据悉，手性分子，用于对映选择性光催化、圆偏振光探测和发射以及分子开关等应用，存在于两种几何构型中，它们是彼此不可重叠的镜像。这些所谓的(R)和(S)对映体在与其他手性实体相互作用时，表现出不同的物理和化学性质。

阿秒技术可能会对这种相互作用产生影响，因为它可以在固有的电子时间标度上探测甚至直接分子内的电子运动，从而控制反应性。光激发手性分子中的电子电流确实被预测可以使分子取向对映敏感，但由于缺乏超短、非电离和微扰光脉冲，中性分子中的电子驱动手性动力学尚未得到证实。

本文利用时间分辨光电子圆二色性(TR-PECD)技术，以前所未有的2.9fs的时间分辨率，绘制了中性手性分子在紫外线激发下的相干电子运动。研究人员发现，里德伯态之间的电子跃迁导致了几飞秒时间尺度上热力响应的周期性调制，并在不到10飞秒的时间尺度上观察到了符号反转的现象。计算验证了这一点，并证实了光致手性电流与圆极化探针脉冲的组合，实现了光电离后分子取向的对映选择性过滤。研究人员期待他们的方法能够进一步深入探索手性体系中的超快电子动力学，为揭示对映敏感电荷定向反应性的机制开辟新途径。

附：英文原文

Title: Capturing electron-driven chiral dynamics in UV-excited molecules

Author: Wanie, Vincent, Bloch, Etienne, Mnsson, Erik P., Colaizzi, Lorenzo, Ryabchuk, Sergey, Saraswathula, Krishna, Ordonez, Andres F., Ayuso, David, Smirnova, Olga, Trabattoni, Andrea, Blanchet, Valrie, Ben Amor, Nadia, Heitz, Marie-Catherine, Mairesse, Yann, Pons, Bernard, Calegari, Francesca

Issue&Volume: 2024-05-22

Abstract: Chiral molecules, used in applications such as enantioselective photocatalysis, circularly polarized light detection and emission and molecular switches, exist in two geometrical configurations that are non-superimposable mirror images of each other. These so-called (R) and (S) enantiomers exhibit different physical and chemical properties when interacting with other chiral entities. Attosecond technology might enable influence over such interactions, given that it can probe and even direct electron motion within molecules on the intrinsic electronic timescale and thereby control reactivity. Electron currents in photoexcited chiral molecules have indeed been predicted to enable enantiosensitive molecular orientation, but electron-driven chiral dynamics in neutral molecules have not yet been demonstrated owing to the lack of ultrashort, non-ionizing and perturbative light pulses. Here we use time-resolved photoelectron circular dichroism (TR-PECD) with an unprecedented temporal resolution of 2.9fs to map the coherent electronic motion initiated by ultraviolet (UV) excitation of neutral chiral molecules. We find that electronic beatings between Rydberg states lead to periodic modulations of the chiroptical response on the few-femtosecond timescale, showing a sign inversion in less than 10fs. Calculations validate this and also confirm that the combination of the photoinduced chiral current with a circularly polarized probe pulse realizes an enantioselective filter of molecular orientations following photoionization. We anticipate that our approach will enable further investigations of ultrafast electron dynamics in chiral systems and reveal a route towards enantiosensitive charge-directed reactivity.

DOI: 10.1038/s41586-024-07415-y

Source: https://www.nature.com/articles/s41586-024-07415-y