JILA, Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309, USA.
Science. 2010 Apr 9;328(5975):220-4. doi: 10.1126/science.1184616. Epub 2010 Mar 4.
Chemical bond breaking involves coupled electronic and nuclear dynamics that can take place on multiple electronic surfaces. Here we report a time-resolved experimental and theoretical investigation of nonadiabatic dynamics during photodissociation of a complex of iodine monobromide anion with carbon dioxide [IBr-(CO2)] on the second excited (A') electronic state. Previous experimental work showed that the dissociation of bare IBr- yields only I- + Br products. However, in IBr-(CO2), time-resolved photoelectron spectroscopy reveals that a subset of the dissociating molecules undergoes an electron transfer from iodine to bromine 350 femtoseconds after the initial excitation. Ab initio calculations and molecular dynamics simulations elucidate the mechanism for this charge hop and highlight the crucial role of the carbon dioxide molecule. The charge transfer between two recoiling atoms, assisted by a single solvent-like molecule, provides a notable limiting case of solvent-driven electron transfer over a distance of 7 angstroms.
化学键的断裂涉及到电子和核的耦合动力学，这可能发生在多个电子表面上。在这里，我们报告了一个关于碘单溴阴离子与二氧化碳[IBr-(CO2)]复合物在第二激发（A'）电子态上光解过程中非绝热动力学的时间分辨实验和理论研究。以前的实验工作表明，裸 IBr-的解离仅产生 I-+Br 产物。然而，在 IBr-(CO2)中，时间分辨光电子能谱揭示了在初始激发 350 飞秒后，一部分解离的分子经历了从碘到溴的电子转移。从头算计算和分子动力学模拟阐明了这种电荷跳跃的机制，并强调了二氧化碳分子的关键作用。两个反冲原子之间的电荷转移，在单个类似溶剂的分子的辅助下，提供了一个显著的限制情况，即在 7 埃的距离上，溶剂驱动的电子转移。
