Xi Hong-Wei, Huang Ming-Bao, Chen Bo-Zhen, Li Wen-Zuo
College of Chemistry and Chemical Engineering, Graduate School, Chinese Academy of Sciences, P.O. Box 4588, Beijing 100049, People's Republic of China.
J Phys Chem A. 2005 May 19;109(19):4381-7. doi: 10.1021/jp050344h.
To examine the experimentally suggested scheme of the pathways for Cl- and H-loss dissociations of the CH(3)Cl(+) ion in the X(2)E (1(2)A', 1(2)A' '), A(2)A(1) (2(2)A'), and B(2)E (3(2)A', 2(2)A") states, the complete active space-self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with an atomic natural orbital (ANO) basis were performed for the 1(2)A' (X(2)A'), 1(2)A", 2(2)A', and 2(2)A'" states. The potential energy curves describing dissociation from the four C(s) states were obtained on the basis of the CASSCF partial geometry optimization calculations at fixed C-Cl or C-H distance values, followed by the CASPT2 energy calculations. The electronic states of the CH3(+) and CH(2)Cl(+) ions produced by Cl-loss and H-loss dissociation, respectively, were carefully determined. Our calculations confirm the following experimental facts: Cl-loss dissociation occurs from the 1(2)A' (X(2)A'), 1(2)A", and 2(2)A' states (all leading to CH3(+) (X(1)A(1)') + Cl), and H-loss dissociation does not occur from 2(2)A'. The calculations indicate that H-loss dissociation occurs from the 1(2)A' and 1(2)A' ' states (leading to CH(2)Cl(+) (X(1)A(1)) + H and CH(2)Cl(+) (1(3)A") + H, respectively). The calculations also indicate that H-loss dissociation occurs (with a barrier) from the 2(2)A" state (leading to CH(2)Cl(+) (1(1)A") + H), supporting the observation of direct dissociation from the B state to CH(2)Cl(+) and that Cl-loss dissociation occurs from the 2(2)A" state (leading to CH3(+) (1(3)A") + Cl), not supporting the previously proposed Cl-loss dissociation of the B state via internal conversion of B to A. The predicted appearance potential values for CH3(+) (X(1)A(1)') and CH(2)Cl(+) (X(1)A(1)) are in good agreement with the experimental values.
为研究实验所提出的X(2)E（1(2)A'，1(2)A''）、A(2)A(1)（2(2)A'）和B(2)E（3(2)A'，2(2)A''）态的CH(3)Cl(+)离子Cl-损失解离和H-损失解离途径方案，使用原子自然轨道（ANO）基组进行了完全活性空间自洽场（CASSCF）和多组态二阶微扰理论（CASPT2）计算，针对1(2)A'（X(2)A'）、1(2)A''、2(2)A'和2(2)A'''态。基于在固定C-Cl或C-H距离值下的CASSCF部分几何优化计算，随后进行CASPT2能量计算，得到了描述从四个C(s)态解离的势能曲线。仔细确定了分别由Cl-损失解离和H-损失解离产生的CH3(+)和CH(2)Cl(+)离子的电子态。我们的计算证实了以下实验事实：Cl-损失解离发生在1(2)A'（X(2)A'）、1(2)A''和2(2)A'态（均导致CH3(+)（X(1)A(1)'）+ Cl），而H-损失解离不发生在2(2)A'态。计算表明H-损失解离发生在1(2)A'和1(2)A''态（分别导致CH(2)Cl(+)（X(1)A(1)）+ H和CH(2)Cl(+)（1(3)A''）+ H）。计算还表明H-损失解离（有势垒）发生在2(2)A''态（导致CH(2)Cl(+)（1(1)A''）+ H），支持了从B态直接解离为CH(2)Cl(+)的观测结果，且Cl-损失解离发生在2(2)A''态（导致CH3(+)（1(3)A''）+ Cl），不支持先前提出的B态通过B到A的内转换进行Cl-损失解离的观点。预测的CH3(+)（X(1)A(1)'）和CH(2)Cl(+)（X(1)A(1)）的出现势值与实验值吻合良好。
