Ring-breaking electron attachment to uracil: following bond dissociations via evolving resonances.
Ring-breaking electron attachment to uracil: following bond dissociations via evolving resonances.
复制标题
破环电子与尿嘧啶的连接：通过不断演化的共振发生键解离。
作者：
F. Gianturco;F. Sebastianelli;R. Lucchese;I. Baccarelli;N. Sanna
在各种不同的能量进行计算，以获得弹性截面和S-矩阵共振指标（极点）从气相尿嘧啶的电子散射的量子处理。低能区证实了π（*）共振的存在，这是由早期的计算和实验所揭示的，与本研究结果进行了比较。结果表明，它们几乎不受键变形的影响，而与较高能量区域（约8 eV）中的sigma（*）共振相关的瞬态负离子（TNI）确实表明，允许多余电子能量振动重新分配到分子靶中的环变形强烈影响这些形状共振：因此，它们沿着沿着不同的解离路径演化，并稳定不同的碎片阴离子。计算结果进一步表明，sigma（*）和pi（*）型势能面（真实的部分）之间的圆锥相交的出现是一个非常可能的机制，负责不同TNI之间的能量转移。这种散射状态的多余电子波函数，一旦映射到分子空间，提供了在环区域中的不同键的选择性断裂的纳米级原因。
Calculations are carried out at various distinct energies to obtain both elastic cross sections and S-matrix resonance indicators (poles) from a quantum treatment of the electron scattering from gas-phase uracil. The low-energy region confirms the presence of pi(*) resonances as revealed by earlier calculations and experiments which are compared with the present findings. They turn out to be little affected by bond deformation, while the transient negative ions (TNIs) associated with sigma(*) resonances in the higher energy region ( approximately 8 eV) indeed show that ring deformations which allow vibrational redistribution of the excess electron energy into the molecular target strongly affect these shape resonances: They therefore evolve along different dissociative pathways and stabilize different fragment anions. The calculations further show that the occurrence of conical intersections between sigma(*) and pi(*)-type potential energy surfaces (real parts) is a very likely mechanism responsible for energy transfers between different TNIs. The excess electron wavefunctions for such scattering states, once mapped over the molecular space, provide nanoscopic reasons for the selective breaking of different bonds in the ring region.