Rotationally inelastic scattering of OH(²π) by HCl(¹Σ). Comparison of experiment and theory

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Universality in the cold and ultra cold dynamics of the barrier less reaction D+ + H2

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A new perspective: imaging the stereochemistry of molecular collisions

The concept of the steric effect in molecular collisions is central to chemistry. In this Perspective article we review some of the progress made in studying the steric effect in inelastic and reactive collisions involving relatively small isolated atomic and molecular species. We overview the theoretical framework used to quantify the steric effect, and outline some of the key experimental approaches that can be employed to study the dynamics and mechanism of collisions involving oriented and aligned molecules. We illustrate the discussion by highlighting a few recent studies of inelastic and reactive scattering. Finally, we conclude with some reflections on possible future directions of interest

Dynamical effects on the O(3P) + D2 reaction and its impact on the Λ-doublet population

11 pags., 9 figs. -- This article is part of the themed collection: Molecular Dynamics in the Gas PhaseThe O(P) + D → OD(Π) + D reaction presents the peculiarity of taking place on two different potential energy surfaces (PESs) of different symmetry, A′ and A′′, which become degenerate for collinear configurations where the saddle-point of the reaction is located. The degeneracy is broken for non-collinear approaches with the energy on the A′ PES rising more abruptly with the bending angle, making the frequency of this mode higher on the A′ state. Consequently, the A′ PES should be less reactive than the A′′ one. Nevertheless, quantum scattering calculations show that the cross section is higher on the A′ PES for energies close to the classical reaction threshold and rotationless reactant. It is found that the differences between the reactivity on the two PESs are greater for low values of total angular momentum, where the centrifugal barrier is lower and contribute to the higher population of the Π(A′) Λ-doublet states of OD at low collision energies. At high collision energies, the Π(A′) Λ-doublet state is also preferentially populated. Analysis of the differential cross sections reveals that the preponderance for the Π(A′) Λ-doublet at low energies comes from backward scattering, originating from the reaction on the A′ PES, while at high energies, it proceeds from a different mechanism that leads to sideways scattering on the A′′ PES and that populates the Π(A′) manifold.The authors gratefully acknowledge grant PID2020-113147GA-I00, PID2021-122839NB-I00, PID2019-107115GB-C21 and PID2021-122549NB-C21 funded by Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/MCIN/AEI/10.13039/501100011033)

Integral steric asymmetry in the inelastic scattering of NO(X2Π)

The integral steric asymmetry for the inelastic scattering of NO(X) by a variety of collision partners was recorded using a crossed molecular beam apparatus. The initial state of the NO(X, v = 0, j = 1/2, Ω=1/2, I=-1,f) molecule was selected using a hexapole electric field, before the NO bond axis was oriented in a static electric field, allowing probing of the scattering of the collision partner at either the N- or O-end of the molecule. Scattered NO molecules were state selectively probed using (1 + 1′) resonantly enhanced multiphoton ionisation, coupled with velocity-map ion imaging. Experimental integral steric asymmetries are presented for NO(X) + Ar, for both spin-orbit manifolds, and Kr, for the spin-orbit conserving manifold. The integral steric asymmetry for spin-orbit conserving and changing transitions of the NO(X) + O2 system is also presented. Close-coupled quantum mechanical scattering calculations employing well-tested ab initio potential energy surfaces were able to reproduce the steric asymmetry observed for the NO-rare gas systems. Quantum mechanical scattering and quasi-classical trajectory calculations were further used to help interpret the integral steric asymmetry for NO + O2. Whilst the main features of the integral steric asymmetry of NO with the rare gases are also observed for the O2 collision partner, some subtle differences provide insight into the form of the underlying potentials for the more complex system

The dynamics of the H+D2O→OD+HD reaction at 2.5 eV: Experiment and theory

10.1063/1.1528896Journal of Chemical Physics11831162-1174JCPS