Reaction dynamics of the methoxy anion CHO with methyl iodide CHI.

Studying larger nucleophiles in bimolecular nucleophilic substitution (S2) reactions bridges the gap from simple model systems to those relevant to organic chemistry. Therefore, we investigated the reaction dynamics between the methoxy anion (CHO) and iodomethane (CHI) in our crossed-beam setup combined with velocity map imaging at the four collision energies 0.4, 0.

Imaging the Ion-Molecule Reaction Dynamics of O + CD.

While neutral reactions involved in methane oxidation have been intensively studied, much less information is known about the reaction dynamics of the oxygen radical anion with methane. Here, we study the scattering dynamics of this anion-molecule reaction using crossed-beam velocity map imaging with deuterated methane. Differential scattering cross sections for the deuterium abstraction channel have been determined at relative collision energies between 0.

Imaging Frontside and Backside Attack in Radical Ion-Molecule Reactive Scattering.

We report on the reactive scattering of methyl iodide, CHI, with atomic oxygen anions O. This radical ion-molecule reaction can produce different ionic products depending on the angle of attack of the nucleophile O on the target molecule. We present results on the backside and frontside attack of O on CHI, which can lead to I and IO products, respectively.

Dynamics of the Oxygen Atom Transfer Reaction between Carbon Dioxide and the Tantalum Cation.

The understanding of fundamental atomic-level processes often requires well-defined model systems. The oxygen atom transfer from CO to a transition metal cation in the gas phase presents such a model system. We investigate the reaction of Ta + CO for which the formation of TaO is highly efficient and attributed to multistate reactivity.

Quasi-classical trajectory study of the OH + CHI reaction: theory meets experiment.

Regarding OH + CHI, several studies have focused on the dynamics of the reaction. Here, high-level quasi-classical trajectory simulations are carried out at four different collision energies on our recently developed potential energy surface. In all, more than half a million trajectories are performed, and for the first time, the detailed quasi-classical trajectory results are compared with the reanalysed crossed-beam ion imaging experiments.

Imaging the Atomistic Dynamics of Single Proton Transfer and Combined Hydrogen/Proton Transfer in the O + CHI Reaction.

We report on reactive scattering studies of the proton transfer and combined hydrogen/proton transfer in the O + CHI reaction. We combine state-of-the-art crossed-beam velocity map imaging and quantum chemistry calculations to understand the dynamics for the formations of the CHI + OH and CHI + HO products. The experimental velocity- and angle-differential cross section show for both products and at all collision energies (between 0.

Atomistic dynamics of elimination and nucleophilic substitution disentangled for the F + CHCHCl reaction.

Chemical reaction dynamics are studied to monitor and understand the concerted motion of several atoms while they rearrange from reactants to products. When the number of atoms involved increases, the number of pathways, transition states and product channels also increases and rapidly presents a challenge to experiment and theory. Here we disentangle the dynamics of the competition between bimolecular nucleophilic substitution (S2) and base-induced elimination (E2) in the polyatomic reaction F + CHCHCl.

Influence of a Supercritical Electric Dipole Moment on the Photodetachment of C_{3}N^{-}.

Threshold photodetachment spectroscopy of the molecular ion C_{3}N^{-} has been performed at both 16(1) and 295(2) K in a 22-pole ion trap. The 295(2) K spectrum shows a large increase in the cross section with an onset about 200  cm^{-1} below threshold, which is explained by significant vibrational excitation of the trapped ions at room temperature. This excitation disappears at cryogenic temperatures leading to an almost steplike onset of the cross section at threshold, which cannot be adequately described with a Wigner threshold law.

Threshold photodetachment spectroscopy of the astrochemical anion CN.

Threshold photodetachment spectroscopy has been performed on the molecular anion CN at both 16(1) K and 295(2) K in a 22-pole ion trap and at 295(2) K from a pulsed ion beam. The spectra show a typical energy dependence of the detachment cross section yielding a determination of the electron affinity of CN to greater precision than has previously been known at 31 163(16) cm [3.864(2) eV].

Influence of Vibrational Excitation on the Reaction of F with CHI: Spectator Mode Behavior, Enhancement, and Suppression.

Detailed insight into chemical reaction dynamics can be obtained by probing the effect of mode-specific vibrational excitation. Suppression or enhancement of reactivity is possible as is already known from the Polanyi rules. In the reaction F + CHI, we found vibrational enhancement, suppression, and spectator mode dynamics in the four different reaction channels.

Proton transfer dynamics modified by CH-stretching excitation.

Gaining insight how specific rovibrational states influence reaction kinetics and dynamics is a fundamental goal of physical chemistry. Purely statistical approaches often fail to predict the influence of a specific state on the reaction outcome, evident in a great number of both experimental and theoretical studies. Most detailed insight in atomistic reaction mechanisms is achieved using accurate collision experiments and high level dynamics calculations.

Imaging Reaction Dynamics of F(HO) and Cl(HO) with CHI.

The dynamics of microhydrated nucleophilic substitution reactions have been studied using crossed beam velocity map imaging experiments and quasiclassical trajectory simulations at different collision energies between 0.3 and 2.6 eV.

Unexpected Indirect Dynamics in Base-Induced Elimination.

Base-induced elimination (E2) and bimolecular nucleophilic substitution (S2) are two of the most versatile reactions that are important in preparative organic chemistry. These stereospecific reactions are often found in direct competition with each other. Elimination can proceed via two distinct transition states, referred to as anti and syn, of which anti is commonly energetically favored.

Conservation of direct dynamics in sterically hindered S2/E2 reactions.

Nucleophilic substitution (S2) and base-induced elimination (E2), two indispensable reactions in organic synthesis, are commonly assumed to proceed under stereospecific conditions. Understanding the way in which the reactants pre-orient in these reactions, that is its stereodynamics, is essential in order to achieve a detailed atomistic picture and control over such processes. Using crossed beam velocity map imaging, we study the effect of steric hindrance in reactions of Cl and CN with increasingly methylated alkyl iodides by monitoring the product ion energy and scattering angle.

Imaging state-to-state reactive scattering in the Ar + H charge transfer reaction.

The charge transfer reaction of Ar with H and D has been investigated in an experiment combining crossed beams with three-dimensional velocity map imaging. Angle-differential cross sections for two collision energies have been obtained for both neutral species. We find that the product ions are highly internally excited.

Imaging dynamic fingerprints of competing E2 and S2 reactions.

The competition between bimolecular nucleophilic substitution and base-induced elimination is of fundamental importance for the synthesis of pure samples in organic chemistry. Many factors that influence this competition have been identified over the years, but the underlying atomistic dynamics have remained difficult to observe. We present product velocity distributions for a series of reactive collisions of the type X + RY with X and Y denoting the halogen atoms fluorine, chlorine and iodine.

Imaging Proton Transfer and Dihalide Formation Pathways in Reactions of F(-) + CH3I.

Ion-molecule reactions of the type X(-) + CH3Y are commonly assumed to produce Y(-) through bimolecular nucleophilic substitution (SN2). Beyond this reaction, additional reaction products have been observed throughout the last decades and have been ascribed to different entrance channel geometries differing from the commonly assumed collinear approach. We have performed a crossed beam velocity map imaging experiment on the F(-) + CH3I reaction at different relative collision energies between 0.