The UV photodissociation of isoxazole (c-C₃H₃NO) is studied in this work by chirped-pulse Fourier transform mm-wave spectroscopy in a pulsed uniform Laval flow. This approach offers a number of advantages over traditional spectroscopic detection methods due to its broadband, sub-MHz resolution, and fast-acquisition capabilities. In coupling this technique with a quasi-uniform Laval flow, we are able to obtain product branching fractions in the 193 nm photodissociation of isoxazole. Five dissociation channels are explored through direct detection of seven different photoproducts. These species and their respective branching fractions (%) include the following: HCN (53.8 ± 1.7), CH₃CN (23.4 ± 6.8), HCO (9.5 ± 2.3), CH₂CN (7.8 ± 2.9), CH₂CO (3.8 ± 0.9), HCCCN (0.9 ± 0.2), and HNC (0.8 ± 0.2). Guided by previous electronic structure and dynamics simulations, we are able to elucidate the dissociation dynamics that govern the final product branching fractions observed in this work, which differ significantly from previous reports on the thermal decomposition of isoxazole. Interestingly, both direct and indirect dynamics contribute to its dissociation, and clear signatures of both are manifested in the relative branching ratios obtained. Consistent with previous studies on the unimolecular dissociation of isoxazole, our findings also suggest the importance of the open-shell singlet diradicaloid species vinylnitrene in the dissociation dynamics, regardless of the initially populated excited state. This work, taken together with previous investigations, provides a global picture of the complex dissociation pathways involved in the photodissociation of isoxazole.

中文翻译：

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产品分支中异恶唑的直接与间接光解离：A脉冲傅里叶变换毫米波光谱/脉冲均匀流研究

在这项工作中，通过chi脉冲傅立叶变换毫米波光谱研究了脉冲均匀拉瓦尔流中异恶唑（cC ₃ H ₃ NO）的紫外光解离。与传统的光谱检测方法相比，该方法具有许多优势，因为它具有宽带，亚MHz分辨率和快速获取功能。通过将此技术与准均匀的Laval流耦合，我们能够在193 nm的异恶唑光解离中获得产物支化级分。通过直接检测七种不同的光产物，探索了五个解离通道。这些种类及其各自的分支分数（％）包括：HCN（53.8±1.7），CH ₃ CN（23.4±6.8），HCO（9.5±2.3），CH ₂CN（7.8±2.9），CH ₂CO（3.8±0.9），HCCCN（0.9±0.2）和HNC（0.8±0.2）。在以前的电子结构和动力学模拟的指导下，我们能够阐明控制该工作中观察到的最终产物支化级分的解离动力学，这与以前关于异恶唑热分解的报道大不相同。有趣的是，直接和间接动力学都有助于其解离，并且在获得的相对支化比中均显示了清晰的特征。与以前对异恶唑单分子解离的研究相一致，我们的发现还表明，不管最初的激发态如何，开壳单线态双自由基类乙烯基亚乙烯基在解离动力学中的重要性。这项工作，加上先前的调查，