Samanta Kousik, Beames Joseph M, Lester Marsha I, Subotnik Joseph E
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
J Chem Phys. 2014 Oct 7;141(13):134303. doi: 10.1063/1.4894746.
The singlet electronic potential energy surfaces for the simplest Criegee intermediate CH2OO are computed over a two-dimensional reduced subspace of coordinates, and utilized to simulate the photo-initiated dynamics on the S2 (B) state leading to dissociation on multiple coupled excited electronic states. The adiabatic electronic potentials are evaluated using dynamically weighted state-averaged complete active space self-consistent field theory. Quasi-diabatic states are constructed from the adiabatic states by maximizing the charge separation between the states. The dissociation dynamics are then simulated on the diabatically coupled excited electronic states. The B ← X electronic transition with large oscillator strength was used to initiate dynamics on the S2 (B) excited singlet state. Diabatic coupling of the B state with other dissociative singlet states results in about 5% of the population evolving to the lowest spin-allowed asymptote, generating H2CO (X (1)A1) and O ((1)D) fragments. The remaining ∼95% of the population remains on repulsive B state and dissociates to H2CO (a (3)A″) and O ((3)P) products associated with a higher asymptotic limit. Due to the dissociative nature of the B state, the simulated electronic absorption spectrum is found to be broad and devoid of any vibrational structure.
针对最简单的克里奇中间体CH2OO，在二维坐标约化子空间上计算了单重态电子势能面，并用于模拟S2(B)态上的光引发动力学，该动力学导致在多个耦合激发电子态上发生解离。使用动态加权态平均完全活性空间自洽场理论评估绝热电子势能。通过最大化态间电荷分离，由绝热态构建准绝热态。然后在绝热耦合激发电子态上模拟解离动力学。利用具有大振子强度的B←X电子跃迁在S2(B)激发单重态上引发动力学。B态与其他解离单重态的绝热耦合导致约5%的布居数演化到最低自旋允许渐近线，生成H2CO(X(1)A1)和O((1)D)碎片。其余约95%的布居数留在排斥性的B态上，并解离为与更高渐近极限相关的H2CO(a(3)A″)和O((3)P)产物。由于B态的解离性质，发现模拟的电子吸收光谱很宽且没有任何振动结构。
