The photochemical pathways of acetanilide and paracetamol were investigated using the XMS-CASPT2 quantum chemical method and the cc-pVDZ (correlation consistent polarized valence double-$\zeta$) basis set. In both compounds, the bright state is the second excited state, designated as a ${}^1({\mathit{\pi \pi }}^{*}$L_a) state. Through a detailed exploration of the potential energy profile and the conical intersection structure between the ${}^1({\mathit{\pi \pi }}^{*}$L_a) and ground states, we gained a better understanding of how cleavage might occur in both molecules upon photoexcitation. Other potential relaxation mechanisms, including crossings with the dark ${}^1\left(n{\pi }^{*}\right)$ and ${}^1({\mathit{\pi \pi }}^{*}$L_a) states, are also discussed in detail.

中文翻译：

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扑热息痛和乙酰苯胺的激发态弛豫机制


使用 XMS-CASPT2 量子化学方法和 cc-pVDZ （相关一致极化价双- $\zeta$ ） 基集研究乙酰苯胺和扑热息痛的光化学途径。在这两种化合物中，亮态是第二激发态，指定为 ${}^1({\mathit{\pi \pi }}^{*}$ L _a ） 态。通过详细探索势能分布以及 ${}^1({\mathit{\pi \pi }}^{*}$ L _a ） 和基态之间的圆锥形交会结构，我们更好地了解了光激发时两个分子如何发生裂解。还详细讨论了其他可能的弛豫机制，包括与暗 ${}^1\left(n{\pi }^{*}\right)$ 态和 ${}^1({\mathit{\pi \pi }}^{*}$ L _a ） 态的交叉。