If a molecular dication is produced on a repulsive potential energy surface (PES), it normally dissociates. Before that, however, ultrafast nuclear dynamics can change the PES and significantly influence the fragmentation pathway. Here, we investigate the electron-impact-induced double ionization and subsequent fragmentation processes of the ethanol molecule using multiparticle coincident momentum spectroscopy and ab initio dynamical simulations. For the electronic ground state of the ethanol dication, we observe several fragmentation channels that cannot be reached by direct Coulomb explosion (CE) but require preceding isomerization. Our simulations show that ultrafast hydrogen or proton transfer (PT) can stabilize the repulsive PES of the dication before the direct CE and form intermediate H₂ or H₂O. These neutrals stay in the vicinity of the precursor, and roaming mechanisms lead to isomerization and finally PT resulting in emission of H₃⁺ or H₃O⁺. The present findings can help to understand the complex fragmentation dynamics of molecular cations.

中文翻译：

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超快速质子传递动力学对乙醇阳离子排斥力的作用：漫游介导的异构化与库仑爆炸。

如果在排斥势能表面（PES）上产生分子指示，则该分子指示通常会解离。但是，在此之前，超快核动力学可以改变PES并显着影响碎片途径。在这里，我们使用多粒子重合动量能谱和从头算动力学模拟研究乙醇分子的电子碰撞诱导的双电离和随后的裂解过程。对于乙醇指示剂的电子基态，我们观察到直接通过库仑爆炸（CE）无法达到但需要事先进行异构化的几个碎裂通道。我们的模拟显示，超快氢或质子转移（PT）可以在直接CE之前稳定离子的排斥性PES并形成中间体H ₂或H_2个O.这些中性粒子留在所述前体的附近，和漫游机制导致异构化和最后PT导致在H发射₃ ⁺或H ₃ ö ⁺。目前的发现可以帮助理解分子阳离子的复杂碎片动力学。