Arenas Juan F, Otero Juan C, Pelaez Daniel, Soto Juan
Department of Physical Chemistry, Faculty of Sciences, University of Malaga, E-29071-Malaga, Spain.
J Phys Chem A. 2005 Aug 18;109(32):7172-80. doi: 10.1021/jp058100k.
The complete active space self-consistent field (CAS-SCF) method combined with the multistate second-order perturbation theory (MS-CASPT2) are used to study the low-lying, singlet and triplet, potential energy surfaces of nitramide. Vertical transition calculations have allowed us to reinterpret the gas-phase UV spectrum of nitramide as the overlapping of two intense bands calculated at 6.46 and 6.52 eV, respectively. The states of relevance in its photochemistry after excitation at different wavelengths have been determined to be up to S4. From that point on, the most probable dissociation mechanism is determined by considering relative energies among the different stationary points and the major role played by conical intersections connecting S3/S2, S2/S1, and S1/S0 electronic states. The most likely dissociation products are NH2(1(2)B1), NO2(1(2)A1), NO2(1(2)A2), NO2(1(2)B2), NO2(1(2)A1)*, NH2NO(1(1)A''), NO(X(2)pi), and O(1D). With regards to the influence of triplet states in the photodecomposition of nitramide, our calculations indicate that T1/S0 crossing is probable only after radiationless deactivation.
采用完全活性空间自洽场（CAS - SCF）方法结合多态二阶微扰理论（MS - CASPT2）来研究硝酰胺的低能单重态和三重态势能面。垂直跃迁计算使我们能够将硝酰胺的气相紫外光谱重新解释为分别在6.46和6.52 eV处计算得到的两个强带的重叠。已确定在不同波长激发后其光化学中相关的态可达S4。从那时起，通过考虑不同驻点之间的相对能量以及连接S3/S2、S2/S1和S1/S0电子态的锥形交叉所起的主要作用来确定最可能的解离机制。最可能的解离产物是NH2(1(2)B1)、NO2(1(2)A1)、NO2(1(2)A2)、NO2(1(2)B2)、NO2(1(2)A1)*、NH2NO(1(1)A'')、NO(X(2)π)和O(1D)。关于三重态在硝酰胺光分解中的影响，我们的计算表明T1/S0交叉仅在无辐射失活后才有可能发生。
