Molecular growth of PANH via intermolecular Coulombic decay

Abstract

Nitrogen-bearing polycyclic aromatic hydrocarbons (PANHs) are ubiquitous in space. They are considered precursors to advanced biomolecules identified in meteorites. However, their chemical evolution into biomolecules in photodestructive astrophysical mediums remains a paradox. Here, we show that light can efficiently initiate the molecular mass growth of PANHs. Ultraviolet-photoexcited quinoline monomers, the smallest PANH, were observed to associate and intermolecular Coulombic decay between the associating monomers formed the cations of quinoline-dimer. Molecular rearrangements in the dimer cation lead to a dominant formation of cations heavier than quinoline. The enrichment of these heavier cations over all the other cations reveals the efficiency of this route for the mass growth of PANHs in space. This mechanism also leads to a highly reactive unsaturated PANH-ring via CH loss, a hitherto unknown channel in any photon-driven process. The occurrence of this efficient pathway toward complex molecules points to a rich chemistry in dense interstellar clouds.

Electron and ion spectroscopy of camphor doped helium nanodroplets in the extreme UV and soft x-ray regime

“…As mentioned previously, the most intense m/q peaks adjacent to the monomer and the oligomer ions up to trimer have missing m/q of 28, corresponding to CO. Additionally, by observing intensities of RY, it is noted that a repetitive pattern appears, such that a camphor molecule forms loose bonds not just with another camphor molecule but with its ionic fragments, too. Photo-association forming oligomers has been recently observed for polycyclic aromatic hydrocarbon (PANH), Quinoline, in gas phase [79] and acetylene molecule in He nanodroplet [55]. Formation of such bonds between a molecule and its ionic fragments requires further scrutiny, which is beyond the scope of this work.…”

Revealing the Role of N Heteroatoms in Noncovalent Aromatic Interactions by Ultrafast Intermolecular Coulombic Decay

“…In the T-shape structure, a CH group is interacting through the H atom with the other ring to form a CH−π interaction. Compared to the numerous existing studies of the benzene dimer, there is a scarcity of investigations of N-containing heteroaromatic dimers especially by experiment, in spite of their clear biochemical importance. − For example, N heteroatoms are prevalent in nucleic acid bases that influence the molecular interaction energies and hence the structures and dynamics of DNA and RNA. − …”

Stimulated Emission of Virtual Photons: Energy Transfer by Light

“…Thus, the excited system as well as the neighbor can be atoms or molecules and the underlying time scale is in the femtosecond regime and becomes faster the more neighbors are present . ICD has many applications ranging from quantum halo systems with an extreme mean separation of the atoms − to quantum dots and wells. − It has been shown to be of potential importance in radiation damage and for molecules of biological interest. − …”