Selective bond formation triggered by short optical pulses: quantum dynamics of a four-center ring closure.
Selective bond formation triggered by short optical pulses: quantum dynamics of a four-center ring closure.
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由短光脉冲触发的选择性键形成：四中心闭环的量子动力学。
DOI：
10.1039/d0cp03435e
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
F. Remacle
中科院分区：
文献类型：
--
作者：
A. Valentini;S. V. D. Wildenberg;F. Remacle
我们报道了超短紫外光脉冲诱导的键的形成。光化学过程被量子动力学描述为超短脉冲诱导降冰片二烯到四环的闭环过程中的相干电子和核运动。降冰片二烯由两个由刚性(CH2)3桥连接的乙烯部分组成。在光激发下，形成两个新的西格玛键，导致四原子环的闭合。降冰片二烯是一种中等大小的多原子分子，在基态以上约6 eV处表现出高密度的强耦合电子态。我们报道了使用短的飞秒紫外光脉冲泵浦开放形式的非平衡电子密度来诱导新键的形成，该电子密度向闭合环形式演化。随着相干电子-核耦合动力学的展开，激发态通过非绝热相互作用改变了性质，成为四环中两个新的C-C键的价态。我们的三维全量子动力学网格模拟表明，不同极化的短紫外光脉冲产生的初始非平衡电子密度明显不同，这些初始非平衡电子密度沿着不同的动力学路径到达S0/S1锥形交点。它们导致了不同的四环烷的初始相对产率，从而为用ATPULSE控制成键开辟了道路。
We report bond formation induced by an ultrashort UV pulse. The photochemical process is described by quantum dynamics as coherent electronic and nuclear motions during the ultrashort pulse induced ring closure of norbornadiene to quadricyclane. Norbornadiene consists of two ethylene moieties connected by a rigid (CH2)3 bridge. Upon photoexcitation, two new sigma bonds are formed, resulting in the closure of a four-atom ring. As a medium-sized polyatomic molecule, norbornadiene exhibits a high density of strongly coupled electronic states from about 6 eV above the ground state. We report on inducing the formation of the new bonds using a short femtosecond UV pulse to pump a non-equilibrium electronic density in the open form that evolves towards the closed ring form. As the coherent electronic-nuclear coupled dynamics unfold, the excited states change character through non-adiabatic interactions and become valence states for the two new C-C bonds of quadricyclane. Our three-dimensional fully quantum dynamical grid simulations during the first 200 fs show that short UV pulses of different polarization initiate markedly different initial non-equilibrium electronic densities that follow different dynamical paths to the S0/S1 conical intersection. They lead to different initial relative yields of quadricyclane, thereby opening the way to controlling bond-making with attopulses.