The roaming chemical reaction mechanism involves near-dissociation of an energized molecule to radicals that leads instead to intramolecular reaction after reorientation at long range. Surprisingly, no clear quantum signatures of roaming have been observed to date, despite the quantum nature of the roaming event. We found evidence of quantum dynamics in the photodissociation of formaldehyde near the roaming threshold. This is ascribed to resonances associated to H+HCO(K_a = 1) that have a profound impact on the CO rotational and translational energy distributions and cause the roaming fraction to vary by a factor of 2 over an energy range of 10 cm^–1. The roaming pathway serves both to modulate and report on the complex vibrational dynamics and coupling among the three dissociation pathways in the excited molecule as it decays to products.

中文翻译：

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甲醛中的轨道共振揭示了漫游、自由基和分子通道的耦合

漫游化学反应机制涉及带电分子接近解离为自由基，从而在远距离重新定向后导致分子内反应。令人惊讶的是，尽管漫游事件具有量子性质，但迄今为止尚未观察到明确的漫游量子特征。我们在漫游阈值附近的甲醛光解中发现了量子动力学的证据。这归因于与 H+HCO( K _a = 1) 相关的共振，它对 CO 旋转和平移能量分布产生深远影响，并导致漫游分数在 10 cm ^{–1的能量范围内变化 2 倍}. 漫游路径用于调节和报告复杂的振动动力学以及在激发分子衰变为产物时三个解离路径之间的耦合。