Observation of molecular motion in a scattering experiment

Kleyn, A.W.; Khromov, V. N.; Los, J.

doi:10.1063/1.439768

Cited by 24 publications

(5 citation statements)

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“…Charge transfer reactions in gas phase evolve in many cases not on a single potential energy surface and are therefore often accompanied by a breakdown of the Born-Oppenheimer approximation. Since the shape of the molecule changes upon charge transfer, state to state electron transfer rates are often controlled by intramolecular vibrational motion [13][14][15]. While in many cases the outcome of a reaction at high collision energies is well described by the properties of the isolated molecule the results at low energies are not explained by a Frank-Condon treatment [16,17].…”

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confidence: 99%

“…Since the shape of the molecule changes upon charge transfer, state to state electron transfer rates are often controlled by intramolecular vibrational motion [13][14][15]. While in many cases the outcome of a reaction at high collision energies is well described by the properties of the isolated molecule the results at low energies are not explained by a Frank-Condon treatment [16,17].…”

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Differential Scattering Cross-Sections for the Different Product Vibrational States in the Ion-Molecule ReactionAr++N2

et al. 2013

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The charge transfer reaction Ar + + N2 → Ar + N + 2 has been investigated in a crossed beam experiment in combination with three-dimensional velocity map imaging. Angular differential stateto-state cross sections were determined as a function of the collision energy. We found that scattering into the first excited vibrational level dominates as expected, but only for scattering in the forward direction. Higher vibrational excitations up to v ′ = 6 have been observed for larger scattering angles. For decreasing collision energy, scattering into higher scattering angles becomes increasingly important for all kinematically allowed quantum states. Our detailed measurements indicate that a quantitative agreement between experiment and theory for this basic ion-molecule reaction now comes within reach.Gas phase studies of ion-molecule reactions have provided insight into a multitude of chemical processes in environments where ions and neutrals coexist. Ion-molecule reactions determine the abundance of many of the complex species that can be detected in interstellar molecular clouds and in planetary atmospheres [1,2]. The conceptually simple charge transfer reactions are particularly interesting, as they were found to explain the X-ray emission from comets [3,4] and may serve as a possible acceleration mechanism of cosmic rays due to strong shock waves in supernova remnants [5]. Charge transfer is also of cosmological importance in that it shapes the hydrogen chemistry in the early universe [6]. Laboratory measurements and theoretical calculations are needed to provide the basis for modeling these processes. In addition charge transfer reactions lead to characteristic light emission from excited states that are useful to determine the parameters of laboratory or technical plasmas, such as temperature, velocity, electron density and charge states of ions [7,8]. To reach very low collision energies, charge transfer has been studied near threshold in half collisions [9]. Recently, ultracold charge transfer reactions have become of interest in studies of cold atom-ion collisions, which are carried out to investigate quantum mechanical phenomena in scattering processes at very low energies [10][11][12].Charge transfer reactions in gas phase evolve in many cases not on a single potential energy surface and are therefore often accompanied by a breakdown of the BornOppenheimer approximation. Since the shape of the molecule changes upon charge transfer, state to state electron transfer rates are often controlled by intramolecular vibrational motion [13][14][15]. While in many cases the outcome of a reaction at high collision energies is well described by the properties of the isolated molecule the results at low energies are not explained by a Frank-Condon treatment [16,17]. This behavior may be explained by molecular bond distortions due to the electric field of the incoming ion [18] and to short range repulsive interactions between the projectile and the target [19].A model system of a gas phase non-Born-Oppenheimer reaction ...

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Differential Scattering Cross-Sections for the Different Product Vibrational States in the Ion-Molecule ReactionAr++N2

et al. 2013

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“…According to equztion (3) this increases the crossing radius, decreases the ionic-covalent interaction, and greatly enhances the probability of the system making a diabatic transition. Since vibration of Br2-is expected to be periodic, the electron affinity and crossing radius will vary with time, and the electron transfer probability at the second crossing will depend on the time required (i.e.. on the speed) for the atomic ion to arrive, as observed experimentally [6]. This effect has been referred to as 'bond stretching'.…”

Section: Theoretical Aspects Of Electron Transfermentioning

confidence: 97%

“…An ideal hexapole field consists of six alternatively charged hyperbolic rods and the electrostatic potential inside this array is given by Downloaded by ["Queen's University Libraries, Kingston"] at 12:08 03 February 2015 (6) where r is the distance from the axis, rL the axial distance to .each electrode, Vo the magnitude of the voltage on the rods, and 4 is the polar angle. (Circular rods are usually used experimentally [ 1 ( d ) ] . )…”

Section: Oriented Molecule Beammentioning

confidence: 99%

Orientation effects in electron transfer collisions

Brooks

1995

International Reviews in Physical Chemistry

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these atoms move in the infinite void, separate one from another and differing in shapes, sizes, position and arrangement; overtaking each other they collided, and some are shaken away in any chance direction, while others, becoming intertwined one with another according to the congruity of their shapes, sizes, positions, and arrangements, stay together and so effect the coming into being of compound bodies.The influence of molecular orientation upon electron transfer has been probed with oriented target molecules in crossed molecular beams. Electron transfer frequently occurs in thermal energy reactive collisions, but at thermal energies charged species can rarely escape their mutual Coulomb attraction, and only neutral products are formed. By increasing the collisional energy to a few eV, the charged species can be separated, and the role of orientation on the electron transfer process can be probed. Collisional ionization of fast ( = 3-20 eV) neutral K atoms has been observed for a variety of symmetric top molecules, such as CH3T, which were oriented in a molecular beam prior to collision. In every case studied so far, the headsltails orientation of the molecule drastically affects the overall probability of ion production. Electron transfer is the first step in ion production; in the second step the ions must get away from one another once formed. Both of these steps can depend on orientation, and the experiments probe the combination of the two. At energies a few volts beyond the threshold, many of the negative ions studied break apart and the orientation dependence seems mainly to be determined by how the ions get away from one another. But the thresholds themselves are orientation dependent, and for the reaction K + CF3Br the threshold for the heads (Br-end) orientation is below the threshold for anion fragmentation. The dominant orientation dependence is mostly in the entrance channel, and for this case we believe the electron is preferentially transferred to the Br end of the molecule.

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“…However, the change in charge state is likely to induce a structural change of the molecule's shape going from the neutral to the ionic species, which affects its vibrational motion. 46,47 Near-resonant channels along the reaction coordinate, which lead to product ions in specific rovibrational states, can result in a break down of the Born-Oppenheimer approximation 48 which makes the accurate theoretical description of the experimental results challenging.…”

Section: Resonances In Ar + Diatom Charge Transfer Reactionsmentioning

confidence: 99%

Imaging the dynamics of ion–molecule reactions

2017

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A range of ion-molecule reactions have been studied in the last years using the crossed-beam ion imaging technique, from charge transfer and proton transfer to nucleophilic substitution and elimination. This review presents the detailed insights that have been gained with respect to the dynamics of both cation-molecule and anion-molecule reactions studied with this method. In particular, we show the recent progress that has been achieved to understand the atomistic energetics and dynamics of ion-molecule reactions, such as the effects of vibrational quantum states, the formation of carbon-carbon bonds, and the competition between nucleophilic substitution and elimination.

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Observation of molecular motion in a scattering experiment

Abstract: The molecular motion in crystalline, plastic, and liquid neopentane studied by cold neutron scattering experiments J. Chem. Phys. 66, 5817 (1977); 10.1063/1.433859Pseudorotational motion of methylcyclopentane observed by neutron inelastic scattering

Cited by 24 publications

References 2 publications

Differential Scattering Cross-Sections for the Different Product Vibrational States in the Ion-Molecule ReactionAr++N2

Differential Scattering Cross-Sections for the Different Product Vibrational States in the Ion-Molecule ReactionAr++N2

Orientation effects in electron transfer collisions

Imaging the dynamics of ion–molecule reactions

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