【摘要】 采用多参考态方法,在MRCI+Q//CAS(10,9)/6-311+G(2df)水平上对叠氮化氰(N3CN)的光解离机理进行理论研究.优化得到基态(S0)和低激发态(S1、S2、T1)势能面上的极小点、过渡态、内转换交叉点(IC-S1/S0)和隙间窜跃交叉点(ISC-S1/T1)的结构和能量,构建反应势能面.在MRCI+Q//CAS(10,9)水平上计算N3CN的垂直激发能,并和实验值进行对比.结果表明,在S0、S1、S2和T1态势能面上,N—N键断裂生成N2+NCN是主要解离途径,而C—N键断裂通道是次要通道.实验观测到220 nm处的吸收峰对应分子由S0态到S1态的激发,对应主要光解离产物为NCN[a1△g];而在275 nm处的吸收峰则对应分子被激发到T1态,然后直接生成基态产物NCN[X3Σg-].我们的理论结果与实验测量符合得很好.更多还原

【Abstract】 We investigated the photodissociation mechanism of cyanogen azide(N3CN) at the MRCI+Q//CAS(10,9)/6-311+G(2df) level of theory using the multi-reference state method.The optimized structures and energies of the minima,transition states,singlet/singlet conical intersection and singlet/triplet crossing points of the ground and low-lying excited states were obtained to explore the potential energy surfaces of N3CN.The vertical excited energies calculated at the MRCI+Q//CAS(10,9) level were compared with the experimental data.It is shown that N—N bond fission to form N2+NCN is the predominant dissociation pathway on the S0,S1,S2,and T1 surfaces whereas the C—N bond fission channel is the minor pathway.The 220 nm absorption peak observed experimentally corresponds to an excitation from the S0 to the S1 state leading to the major photodissociation product NCN[a1△g].The 275 nm absorption peak corresponds to the S0-T1 transition leading to the formed ground-state product NCN [X 3Σg-] via the barrierlessly direct dissociation in the T1 state.Our theoretical results agree well with experimental observations.更多还原