Gope Krishnendu, Livshits Ester, Bittner Dror M, Baer Roi, Strasser Daniel
Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Fritz Haber Research Center for Molecular Dynamics and the Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Sci Adv. 2022 Sep 30;8(39):eabq8084. doi: 10.1126/sciadv.abq8084. Epub 2022 Sep 28.
Electron-transfer reactions are ubiquitous in chemistry and biology. The electrons' quantum nature allows their transfer across long distances. For example, in the well-known harpoon mechanism, electron transfer results in Coulombic attraction between initially neutral reactants, leading to a marked increase in the reaction rate. Here, we present a different mechanism in which electron transfer from a neutral reactant to a multiply charged cation results in strong repulsion that encodes the electron-transfer distance in the kinetic energy release. Three-dimensional coincidence imaging allows to identify such "inverse" harpoon products, predicted by nonadiabatic molecular dynamics simulations to occur between H and HCOH following double ionization of isolated methanol molecules. These dynamics are experimentally initiated by single-photon double ionization with ultrafast extreme ultraviolet pulses, produced by high-order harmonic generation. A detailed comparison of measured and simulated data indicates that while the relative probability of long-range electron-transfer events is correctly predicted, theory overestimates the electron-transfer distance.
电子转移反应在化学和生物学中无处不在。电子的量子特性使其能够远距离转移。例如，在著名的“鱼叉”机制中，电子转移导致初始呈中性的反应物之间产生库仑引力，从而使反应速率显著提高。在此，我们提出一种不同的机制，即从中性反应物到多电荷阳离子的电子转移会产生强烈的斥力，该斥力将电子转移距离编码在动能释放中。三维符合成像能够识别此类“反向”鱼叉产物，非绝热分子动力学模拟预测在孤立甲醇分子双电离后，氢（H）与甲醛（HCOH）之间会出现这种产物。这些动力学过程通过高次谐波产生的超快极紫外脉冲进行单光子双电离在实验中引发。实测数据与模拟数据的详细比较表明，虽然远程电子转移事件的相对概率得到了正确预测，但理论高估了电子转移距离。
