Understanding of the fundamental mechanisms involved in the decomposition of 1,3,5‐trinitro‐1,3,5‐triazinane (RDX) still represents a major challenge for the energetic materials and physical (organic) chemistry communities mainly because multiple competing dissociation channels are likely involved and previous detection methods of the products are not isomer selective. In this study we exploited a microsecond pulsed infrared laser to decompose thin RDX films at 5 K under mild conditions to limit the fragmentation channels. The subliming decomposition products during the temperature programed desorption phase are detected using isomer selective single photoionization time‐of‐flight mass spectrometry (PI‐ReTOF‐MS). This technique enables us to assign a product signal at m/z=42 to ketene (H₂CCO), but not to diazomethane (H₂CNN; 42 amu) as speculated previously. Electronic structure calculations support our experimental observations and unravel the decomposition mechanisms of RDX leading eventually to the elusive ketene (H₂CCO) via an exotic, four‐membered ring intermediate. This study highlights the necessity to exploit isomer‐selective detection schemes to probe the true decomposition products of nitramine‐based energetic materials.

中文翻译：

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固体1,3,5-Trinitro-1,3,5-Triazinane（RDX）的红外多光子离解中的难以捉摸的Ketene（H2 CCO）通道。

对1,3,5-三硝基-1,3,5-三氮杂烷（RDX）分解所涉及的基本机理的理解仍然是高能材料和物理（有机）化学社区面临的主要挑战，主要是因为存在多个竞争的解离通道可能涉及到这些产物，并且以前的产物检测方法对异构体没有选择性。在这项研究中，我们利用微秒脉冲红外激光在温和条件下在5 K下分解RDX薄膜，以限制碎片通道。使用异构体选择性单光电离飞行时间质谱（PI‐ReTOF‐MS）检测程序升温脱附阶段中的升华分解产物。该技术使我们能够将m / z = 42的产物信号分配给烯酮（H ₂CCO），但不是先前推测的重氮甲烷（H ₂ CNN； 42 amu）。电子结构计算支持我们的实验观察，并揭示了RDX通过异乎寻常的四元环中间体最终导致难以捉摸的烯酮（H ₂ CCO）的分解机理。这项研究强调了利用异构体选择性检测方案来探测基于硝胺的高能材料真正分解产物的必要性。