Monomer size effect in inelastic collisional dynamics of non-equilibrium soot nucleation.

Molecular dynamics (MD) simulations of the collisional dynamics of the coronene-acepyrene and coronene radical-acepyrene pairs have been carried out to investigate the size effect of monomers of polycyclic aromatic hydrocarbons (PAH) on their non-equilibrium dimerization. The results compared to the previous MD simulations of the smaller pyrene-acepyrene and pyrenyl-acepyrene systems corroborate the non-equilibrium hypothesis of crosslinking PAH dimerization enhanced by physical interaction between the monomers. The phenomenon of inelastic collisional dynamics responsible for non-equilibrium van der Waals dimerization, which fosters a covalent bond formation between the monomers, amplifies with increasing PAH size.

Low-temperature gas-phase formation of cyclopentadiene and its role in the formation of aromatics in the interstellar medium.

The cyclopentadiene (CH) molecule has emerged as a molecular building block of nonplanar polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanostructures such as corannulene (CH), nanobowls (CH), and fullerenes (C) in deep space. However, the underlying elementary gas-phase processes synthesizing cyclopentadiene from acyclic hydrocarbon precursors have remained elusive. Here, by merging crossed molecular beam experiments with rate coefficient calculations and comprehensive astrochemical modeling, we afford persuasive testimony on an unconventional low-temperature cyclization pathway to cyclopentadiene from acyclic precursors through the reaction of the simplest diatomic organic radical-methylidyne (CH)-with 1,3-butadiene (CH) representing main route to cyclopentadiene observed in TaurusMolecular Cloud.

Experimental and theoretical study of the Sn-O bond formation between atomic tin and molecular oxygen.

The merging of the electronic structure calculations and crossed beam experiments expose the reaction dynamics in the tin (Sn, P) - molecular oxygen (O, XΣ-g) system yielding tin monoxide (SnO, XΣ) along with ground state atomic oxygen O(P). The reaction can be initiated on the triplet and singlet surfaces addition of tin to the oxygen atom leading to linear, bent, and/or triangular reaction intermediates. On both the triplet and singlet surfaces, formation of the tin dioxide structure is required prior to unimolecular decomposition to SnO(XΣ) and O(P).

Interstellar Formation of Nitrogen Heteroaromatics [Indole, CHN; Pyrrole, CHN; Aniline, CHNH]: Key Precursors to Amino Acids and Nucleobases.

Nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) are not only fundamental building blocks in the prebiotic synthesis of vital biomolecules such as amino acids and nucleobases of DNA and RNA but also a potential source of the prominent unidentified 6.2 μm interstellar absorption band. Although NPAHs have been detected in meteorites and are believed to be ubiquitous in the universe, their formation mechanisms in deep space have remained largely elusive.

Gas-Phase Structures of Fucosylated Oligosaccharides: Alkali Metal and Halogen Influences.

Fucosylated carbohydrate antigens play critical roles in physiology and pathology with function linked to their structural details. However, the separation and structural characterization of isomeric fucosylated epitopes remain challenging analytically. Here, we report for the first time the influence of alkali metal cations (Li, Na, K, Rb, and Cs) and halogen anions (Cl, Br, and I) on the gas-phase conformational landscapes of common fucosylated trisaccharides (Lewis A, X, and H types 1 and 2) and tetrasaccharides (Lewis B and Y) using trapped ion mobility spectrometry coupled to mass spectrometry and theoretical calculations.