A novel ethynyl addition mechanism (EAM) has been established computationally as a practicable alternative to high-temperature hydrogen-abstraction-C2H2-addition (HACA) sequences to form polycyclic aromatic hydrocarbon (PAH) -like species under low-temperature conditions in the interstellar medium and in hydrocarbon-rich atmospheres of planets and their moons. Initiated by an addition of the et...

The reaction of ground-state ethynyl radicals, C(2)H(X(2)Sigma(+)), with d(4)-ethylene, C(2)D(4)(X(1)A(g)), was investigated at a collision energy of 20.6 +/- 0.4 kJ mol(-1) utilizing the crossed-beams technique. Combined with electronic structure calculations, our results elucidate that this reaction follows indirect reaction dynamics via a doublet radical complex. The reaction is initiated by...

Symmetric and nonsymmetric hydrogen abstraction reactions are studied using state-of-the-art ab initio electronic structure methods. Second-order Møller-Plesset perturbation theory (MP2) and the coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] methods with large correlation consistent basis sets (cc-pVXZ, where X = D,T,Q) are used in determining the transition-state geometri...

The Zeeman splitting that a longitudinal magnetic field would produce on the ethynyl radical is calculated for the transitions typical of those observed in the interstellar clouds. It turns out that the ubiquitous CCH radical adds to the list of the few interstellar molecules that could be used to determine magnetic fields in molecular clouds.

Polycyclic aromatic hydrocarbons and related species have been suggested to play a key role in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest building block--the aromatic benzene molecule--has remained elusive for decades. Here we demonstrate in crossed molecular beam experiments combined with electronic structure and statistical calcu...

A series of linkers constructed from combinations of phenyl and ethynyl groups is shown to permit ultrafast energy transfer between two chlorophylls, while allowing control over radical cation migration between them.

The crossed beams reaction of ground state ethynyl radicals, C2H(X S), with allene, H2CCCH2(X A1), was conducted under single collision conditions at a collision energy of 22.0 0.4 kJ mol. The center-of-mass functions were combined with earlier ab initio calculations and revealed that the reaction was barrier-less, proceeded via indirect reaction dynamics through an addition of the ethynyl radi...