Barik Saroj, Dutta Saurav, Behera Nihar Ranjan, Kushawaha Rajesh Kumar, Sajeev Y, Aravind G
Department of Physics, Indian Institute of Technology Madras, Chennai, India.
Physical Research Laboratory, Ahmedabad, India.
Nat Chem. 2022 Oct;14(10):1098-1102. doi: 10.1038/s41557-022-01002-2. Epub 2022 Jul 31.
Intermolecular Coulombic decay (ICD) is a process whereby photoexcited molecules relax by ionizing their neighbouring molecules. ICD is efficient when intermolecular interactions are active and consequently it is observed only in weakly bound systems, such as clusters and hydrogen-bonded systems. Here we report an efficient ICD between unbound molecules excited at ambient-light intensities. On the photoexcitation of gas-phase pyridine monomers, well below the ionization threshold and at low laser intensities, we detected the parent and heavier-than-parent cations. The isotropic emission of slow electrons revealed ICD as the underlying process. π-π* excitation in unbounded pyridine monomers triggered an associative interaction between them, which leads to an efficient three-centre ICD. The cation resulting from the molecular association of the three pyridine centres relaxed through fragmentation. This below-threshold ionization under ambient light has implications for the understanding of radiation damage and astrochemistry.
分子间库仑衰变（ICD）是一种光激发分子通过使相邻分子电离而弛豫的过程。当分子间相互作用活跃时，ICD是有效的，因此它仅在弱束缚体系中被观测到，例如团簇和氢键体系。在此，我们报道了在环境光强度下激发的未结合分子之间的高效ICD。在远低于电离阈值且激光强度较低的情况下，对气相吡啶单体进行光激发时，我们检测到了母体阳离子和比母体重的阳离子。慢电子的各向同性发射揭示了ICD是其潜在过程。未结合的吡啶单体中的π-π*激发引发了它们之间的缔合相互作用，这导致了高效的三中心ICD。由三个吡啶中心的分子缔合产生的阳离子通过碎片化弛豫。这种环境光下的阈值以下电离对于理解辐射损伤和天体化学具有重要意义。
