The dissociation of the simplest Criegee intermediate (H\(_2\)COO) into formaldehyde (H\(_2\)CO) and oxygen atom (O) is very important in the atmospheric chemistry. In this study, we investigate the photodissociation of the O–O bond of H\(_2\)COO by simulating the dynamics of the process on the fitted multiconfigurational adiabatic potential energy surfaces (PESs). Tully’s fewest-switches surface hopping (FSSH) method is used for the simulation. The FSSH trajectories are initiated on the lowest optically-bright singlet excited state (\(S_2\)) and propagated along the O–O coordinate. Some of the trajectories end up on energetically lower PESs as a result of radiationless transfer through conical intersections. However, all the trajectories lead to O–O bond dissociation via one of the two channels. The simulation results demonstrate that the restricted O–O motion dissociates H\(_2\)COO into singlet fragments via the lower energy channel. The coupling of electronic states along O–O may account for this.

Graphical abstract

The photodissociation of simplest Criegee intermediate (H₂COO) into formaldehyde (H₂CO) and oxygen (O) was studied using Tully's fewest-switches surface hopping (FSSH). The simulation results demonstrate that the restricted O–O motion dissociates into singlet fragments via the lower energy channel.

中文翻译：

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最简单的 Criegee 中间体中的光解离途径：半经典研究

最简单的 Criegee 中间体 (H \(_2\) COO) 解离为甲醛 (H \(_2\) CO) 和氧原子 (O) 在大气化学中非常重要。在本研究中，我们通过模拟拟合的多构型绝热势能面（PES）上的过程动力学，研究了 H \(_2\) COO的 O-O 键的光解离。Tully 的最少开关表面跳跃 (FSSH) 方法用于模拟。FSSH 轨迹在最低光学亮度单重激发态 ( \(S_2\)）并沿 O-O 坐标传播。由于通过圆锥形交叉点的无辐射传输，一些轨迹最终处于能量较低的 PES 上。然而，所有轨迹都会通过两个通道之一导致 O-O 键解离。模拟结果表明，受限的 O-O 运动通过较低的能量通道将 H \(_2\) COO 解离成单线态片段。电子态沿 O-O 的耦合可以解释这一点。

图形概要

使用塔利最少开关表面跳跃 (FSSH) 研究了最简单的Criegee 中间体 (H ₂ COO) 光解成甲醛 (H _{2 CO) 和氧气 (O)。}模拟结果表明，受限的 O-O 运动通过较低的能量通道解离成单线态片段。