Time resolved mechanism of the isotope selectivity in the ultrafast light induced dissociation in N2.
Time resolved mechanism of the isotope selectivity in the ultrafast light induced dissociation in N2.
复制标题
N2 中超快光诱导解离同位素选择性的时间分辨机制。
DOI：
10.1063/1.5118990
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
R. Levine
中科院分区：
文献类型：
--
作者：
K. Komarova;F. Remacle;R. Levine
用量子力学模拟方法研究了真空紫外光激发N2分子从超快激发到解离的时间演化。主要目的是辨别的作用，激发脉冲短的振动周期相比，辨别不同的电子状态，非绝热，自旋轨道之间的不同耦合机制，并分析任何同位素效应的起源。我们比较了时间和能量域的图像。最初的超快激发泵的分子到一个相干的电子波包，几个单重束缚电子态的贡献。总的非定常波函数被给出为每个电子态上的原子核波包的相干和乘以定常电子波函数。当不同电子态上的波包重叠时，无论使用绝热或非绝热电子基，它们都以质量相关的方式耦合。弱的自旋轨道耦合作为相空间的束缚单重态部分和发生解离的三重态流形之间的瓶颈。为了描述随时间变化的自旋-轨道微扰，能量分辨本征态表象似乎更直观。在本征态的基础上，单重态到三重态的布居转移是大的，只有那些准共振的能量的振动本征态之间。在不同的激发能量范围内，共振态是不同的。共振是质量依赖性的，这解释了通过脉冲的轮廓对同位素效应的控制。
The time evolution of a vacuum ultraviolet excited N2 molecule is followed all the way from an ultrafast excitation to dissociation by a quantum mechanical simulation. The primary aim is to discern the role of the excitation by a pulse short compared to the vibrational period, to discern the different coupling mechanisms between different electronic states, nonadiabatic, spin orbit, and to analyze the origin of any isotopic effect. We compare the picture in the time and energy domains. The initial ultrafast excitation pumps the molecule to a coherent electronic wave packet to which several singlet bound electronic states contribute. The total nonstationary wave function is given as a coherent sum of nuclear wave packets on each electronic state times the stationary electronic wave function. When the wave packets on different electronic states overlap, they are coupled in a mass-dependent manner whether one uses an adiabatic or a diabatic electronic basis. A weak spin-orbit coupling acts as a bottleneck between the bound singlet part of phase space and the triplet manifold of states in which dissociation takes place. To describe the spin-orbit perturbation that is ongoing in time, an energy-resolved eigenstate representation appears to be more intuitive. In the eigenstate basis, the singlet-to-triplet population transfer is large only between those vibronic eigenstates that are quasiresonant in energy. The states in resonance are different for different excitation energy ranges. The resonances are mass dependent, which explains the control of the isotope effect through the profile of the pulse.