The photochemical decomposition of 4-methoxyphenyl azide (CH₃O-Ph-N₃) is investigated using multiconfigurational second-order perturbation theory (MS-CASPT2). In addition, the multi-state resonance Raman spectra of the reactant, intermediates, and product are computed with a multi-state version of the vibronic theory of Albrecht. The results support that the key step of the photolysis of the parent azide is a 2¹A′/2³A′′ intersystem crossing which in a second step decays through a 2³A′′/1³A′′ conical intersection to give directly the formation of triplet 4-methoxyphenyl nitrene (CH₃O-Ph-N) in its lowest electronic state, 1³A′′. It is found that the efficiency of the cited intersystem crossing is enhanced by the close presence of a 2¹A′/2¹A′′ conical intersection. On the other hand, the calculated spectra suggest that the only two species which would be observed in the gas phase experiments are the triplet nitrene plus 4,4′-dimethoxyazobenzene.

中文翻译：

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MS-CASPT2研究4-甲氧基苯基叠氮化物的光分解：内部转化和系统间交叉的作用†

使用多构型二级扰动理论（MS-CASPT2）研究了4-甲氧基苯基叠氮化物（CH ₃ O-Ph-N ₃）的光化学分解。此外，反应物，中间体和产物的多态共振拉曼光谱是用Albrecht振动理论的多态形式计算的。结果表明，母体叠氮化物光解的关键步骤是2 ¹ A'/ 2 ³ A''系统间交叉，第二步通过2 ³ A''/ 1 ³ A''圆锥形交点衰减至直接以最低的电子态1 ³形成三重态4-甲氧基苯基腈（CH ₃ O-Ph-N）一个''。发现通过紧密存在2 ¹ A'/ 2 ¹ A''圆锥形相交点来提高所引用的系统间相交的效率。另一方面，计算的光谱表明，在气相实验中将观察到的仅有的两种物种是三重态氮烯加上4,4'-二甲氧基偶氮苯。