Muchová E, Gopakumar G, Unger I, Öhrwall G, Céolin D, Trinter F, Wilkinson I, Chatzigeorgiou E, Slavíček P, Hergenhahn U, Winter B, Caleman C, Björneholm O
Department of Physical Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28, Prague, Czech Republic.
Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden.
Nat Commun. 2024 Oct 16;15(1):8903. doi: 10.1038/s41467-024-52740-5.
Charge transfer between molecules lies at the heart of many chemical processes. Here, we focus on the ultrafast electron dynamics associated with the formation of charge-transfer-to-solvent (CTTS) states following X-ray absorption in aqueous solutions of Na, Mg, and Al ions. To explore the formation of such states in the aqueous phase, liquid-jet photoemission spectroscopy is employed. Using the core-hole-clock method, based on Auger-Meitner (AM) decay upon 1s excitation or ionization of the respective ions, upper limits are estimated for the metal-atom electron delocalization times to the neighboring water molecules. These delocalization processes represent the first steps in the formation of hydrated electrons, which are determined to take place on a timescale ranging from several hundred attoseconds (as) below the 1s ionization threshold to only 20 as far above the 1s ionization threshold. The decrease in the delocalization times as a function of the photon energy is continuous. This indicates that the excited electrons remain in the vicinity of the studied ions even above the ionization threshold, i.e., metal-ion electronic resonances associated with the CTTS state manifolds are formed. The three studied isoelectronic ions exhibit quantitative differences in their electron energetics and delocalization times, which are linked to the character of the respective excited states.
分子间的电荷转移是许多化学过程的核心。在此，我们聚焦于在钠、镁和铝离子的水溶液中进行X射线吸收后，与电荷转移至溶剂（CTTS）态形成相关的超快电子动力学。为了探究水相中此类状态的形成，我们采用了液体喷射光发射光谱法。利用基于各离子1s激发或电离时俄歇 - 迈特纳（AM）衰变的芯孔时钟法，估算了金属原子电子离域到相邻水分子的时间上限。这些离域过程代表了水合电子形成的第一步，经测定，其发生时间尺度范围从低于1s电离阈值时的几百阿秒（as）到远高于1s电离阈值时的仅20阿秒。离域时间随光子能量的降低是连续的。这表明即使在电离阈值以上，激发电子仍保留在所研究离子的附近，即形成了与CTTS态流形相关的金属离子电子共振。所研究的三种等电子离子在电子能量学和离域时间上表现出定量差异，这与各自激发态的特性相关。
