Dicyanoacetylene (NCN) Formation in the CN + Cyanoacetylene (HCN) Reaction: A Combined Crossed-Molecular Beams and Theoretical Study.

Unsaturated nitriles are significant in prebiotic and astrochemistry. Dicyanoacetylene, in particular, is a possible precursor of uracil and was previously detected in Titan's atmosphere. Its null dipole moment hindered detection through rotational spectroscopy in interstellar clouds, and it escaped identification until recently, when its protonated form NCNH was finally detected toward the Taurus molecular cloud (TMC-1) (Agúndez et al.

A combined crossed molecular beam and theorerical study of the O(P,D) + acrylonitrile (CHCHCN) reactions and implications for combustion and extraterrestrial environments.

Acrylonitrile (CHCHCN) is ubiquitous in space (molecular clouds, solar-type star forming regions, and circumstellar envelopes) and is also abundant in the upper atmosphere of Titan. The reaction O(P) + CHCHCN can be of relevance in the chemistry of the interstellar medium because of the abundance of atomic oxygen. The oxidation of acrylonitrile is also important in combustion as the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including acrylonitrile.

OH(Π) + CH Reaction: A Combined Crossed Molecular Beam and Theoretical Study.

The reaction between the ground-state hydroxyl radical, OH(Π), and ethylene, CH, has been investigated under single-collision conditions by the crossed molecular beam scattering technique with mass-spectrometric detection and time-of-flight analysis at the collision energy of 50.4 kJ/mol. Electronic structure calculations of the underlying potential energy surface (PES) and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of product branching fractions on the derived PES for the addition pathway have been performed.

Reactions O(P, D) + HCCCN(XΣ) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments.

Cyanoacetylene HCCCN), the first member of the cyanopolyyne family (HCN, where = 3, 5, 7, ...

Reaction N(D) + CHCCH (Allene): An Experimental and Theoretical Investigation and Implications for the Photochemical Models of Titan.

We report on a combined experimental and theoretical investigation of the N(D) + CHCCH (allene) reaction of relevance in the atmospheric chemistry of Titan. Experimentally, the reaction was investigated (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy ( ) of 33 kJ/mol to determine the primary products and the reaction micromechanism and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 to 296 K. Theoretically, electronic structure calculations of the doublet CHN potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism.

Intersystem crossing in the entrance channel of the reaction of O(P) with pyridine.

Two quantum effects can enable reactions to take place at energies below the barrier separating reactants from products: tunnelling and intersystem crossing between coupled potential energy surfaces. Here we show that intersystem crossing in the region between the pre-reactive complex and the reaction barrier can control the rate of bimolecular reactions for weakly coupled potential energy surfaces, even in the absence of heavy atoms. For O(P) plus pyridine, a reaction relevant to combustion, astrochemistry and biochemistry, crossed-beam experiments indicate that the dominant products are pyrrole and CO, obtained through a spin-forbidden ring-contraction mechanism.

The N(D) + CHCHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan.

The reaction of electronically excited nitrogen atoms, N(D), with vinyl cyanide, CHCHCN, has been investigated under single-collision conditions by the crossed molecular beam (CMB) scattering method with mass spectrometric detection and time-of-flight (TOF) analysis at the collision energy, , of 31.4 kJ/mol. Synergistic electronic structure calculations of the doublet potential energy surface (PES) have been performed to assist in the interpretation of the experimental results and characterize the overall reaction micromechanism.

The Reaction N(D) + CHCCH (Methylacetylene): A Combined Crossed Molecular Beams and Theoretical Investigation and Implications for the Atmosphere of Titan.

The reaction of excited nitrogen atoms N(D) with CHCCH (methylacetylene) was investigated under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy () of 31.0 kJ/mol. Synergistic electronic structure calculations of the doublet potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction micromechanism.

Leading Interaction Components in the Structure and Reactivity of Noble Gases Compounds.

The nature, strength, range and role of the bonds in adducts of noble gas atoms with both neutral and ionic partners have been investigated by exploiting a fine-tuned integrated phenomenological-theoretical approach. The identification of the leading interaction components in the noble gases adducts and their modeling allows the encompassing of the transitions from pure noncovalent to covalent bound aggregates and to rationalize the anomalous behavior (deviations from noncovalent type interaction) pointed out in peculiar cases. Selected adducts affected by a weak chemical bond, as those promoting the formation of the intermolecular halogen bond, are also properly rationalized.