UV Photodissociation Dynamics of the Acetone Oxide Criegee Intermediate: Experiment and Theory
UV Photodissociation Dynamics of the Acetone Oxide Criegee Intermediate: Experiment and Theory
复制标题
氧化丙酮 Criegee 中间体的紫外光解动力学：实验与理论
DOI：
10.1039/d3cp00207a
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发表时间：
2023
影响因子：
3.3
通讯作者：
Lester, Marsha I
中科院分区：
文献类型：
--
作者：
Wang, Guanghan;Liu, Tianlin;Zou, Meijun;Karsili, Tolga;Lester, Marsha I
二甲基取代的氧化丙酮Criegee中间体[(CH3)2COO]在电子激发到明亮的1π *态后，得到了O (1D) +丙酮[(CH3)2CO， S0]的光解动力学。在喷射冷却条件下，O （1D）检测记录的（CH3）2COO的紫外作用谱宽，无结构，与用紫外诱导耗尽法获得的相应电子吸收光谱基本不变。这表明（CH3）2COO的紫外激发主要导致O （1D）产物通道。没有观察到能量更高的O (3P) + (CH3)2CO （T1）产物通道，尽管它在能量上是可接近的。此外，互补的MS-CASPT2轨迹表面跳跃（TSH）模拟表明，最小的种群导致O （3P）通道和非统一的总体解离概率（在100秒内）。利用O （1D）产物的速度图成像，揭示了（CH3）2COO在不同紫外激发能下光解时的总动能释放（TKER）分布。TKER分布的模拟使用混合模型进行，该模型结合了脉冲模型和统计成分，后者反映了TSH计算中确定的较长寿命（bbb100 fs）轨迹。脉冲模型考虑了Criegee中间体和羰基产物之间的几何变化引起的（CH3）2CO的振动活化，表明CO拉伸、CCO弯曲和CC拉伸以及（CH3）2CO产物中甲基的受阻旋转和岩石活化的重要性。并与紫外激发下ch220光解动力学引起的TKER分布作了详细的比较。
The photodissociation dynamics of the dimethyl-substituted acetone oxide Criegee intermediate [(CH3)2COO] is characterized following electronic excitation to the bright 1ππ* state, which leads to O (1D) + acetone [(CH3)2CO, S0] products. The UV action spectrum of (CH3)2COO recorded with O (1D) detection under jet-cooled conditions is broad, unstructured, and essentially unchanged from the corresponding electronic absorption spectrum obtained using a UV-induced depletion method. This indicates that UV excitation of (CH3)2COO leads predominantly to the O (1D) product channel. A higher energy O (3P) + (CH3)2CO (T1) product channel is not observed, although it is energetically accessible. In addition, complementary MS-CASPT2 trajectory surface-hopping (TSH) simulations indicate minimal population leading to the O (3P) channel and non-unity overall probability for dissociation (within 100 fs). Velocity map imaging of the O (1D) products is utilized to reveal the total kinetic energy release (TKER) distribution upon photodissociation of (CH3)2COO at various UV excitation energies. Simulation of the TKER distributions is performed using a hybrid model that combines an impulsive model with a statistical component, the latter reflecting the longer-lived (>100 fs) trajectories identified in the TSH calculations. The impulsive model accounts for vibrational activation of (CH3)2CO arising from geometrical changes between the Criegee intermediate and the carbonyl product, indicating the importance of CO stretch, CCO bend, and CC stretch along with activation of hindered rotation and rock of the methyl groups in the (CH3)2CO product. Detailed comparison is also made with the TKER distribution arising from photodissociation dynamics of CH2OO upon UV excitation.