Understanding the quantum nature of low-energy C(P ) + He inelastic collisions.

Inelastic collisions that occur between open-shell atoms and other atoms or molecules, and that promote a spin-orbit transition, involve multiple interaction potentials. They are non-adiabatic by nature and cannot be described within the Born-Oppenheimer approximation; in particular, their theoretical modelling becomes very challenging when the collision energies have values comparable to the spin-orbit splitting. Here we study inelastic collisions between carbon in its ground state C(P) and helium atoms-at collision energies in the vicinity of spin-orbit excitation thresholds (~0.

Comparative experimental and theoretical study of the rotational excitation of CO by collision with ortho- and para-D molecules.

A joint crossed beam and quantum mechanical investigation of the rotationally inelastic collisions of CO with ortho- and para-D molecules is reported. A new 4D potential energy surface (PES) averaged over the ground vibrational states of D and CO is used to calculate the rovibrational bound states of the ortho-D-CO complexes. Close coupling calculations are then performed in the rigid rotor approximation for ortho- and para-D colliding with CO for the experimentally investigated transition of CO (j = 0 → 1) and for collision energies ranging from 0.

S((1)D) + ortho-D2 Reaction Dynamics at Low Collision Energies: Complementary Crossed Molecular Beam Experiments and Theoretical Investigations.

The excitation function of the S((1)D) + D2 reaction was determined in a crossed molecular beam apparatus for collision energies ranging from 1817 to 47 J mol(-1) in the near-cold regime. A very good overall agreement was found between experimental data and the theoretical results obtained using the ab initio potential energy surface built by Ho and coworkers and different methods: time-independent quantum dynamics (QM), semiclassical mean potential capture theory (sc-MPCT), and quasi-classical trajectories (QCT). The general trend of the experimental excitation function is well reproduced in most of the range by a simple capture calculation with an R(-6) dispersion potential.

Imaging resonances in low-energy NO-He inelastic collisions.

In molecular collisions, resonances occur at specific energies at which the colliding particles temporarily form quasibound complexes, resulting in rapid variations in the energy dependence of scattering cross sections. Experimentally, it has proven challenging to observe such scattering resonances, especially in differential cross sections. We report the observation of resonance fingerprints in the state-to-state differential cross sections for inelastic NO-He collisions in the 13 to 19 centimeter(-1) energy range with 0.

Reactions of State-Selected Atomic Oxygen Ions O(+)((4)S, (2)D, (2)P) with Methane.

An experimental study has been carried out on the reactions of state selected O(+)((4)S, (2)D, (2)P) ions with methane with the aims of characterizing the effects of both the parent ion internal energy and collision energy on the reaction dynamics and determining the fate of oxygen species in complex media, in particular the Titan ionosphere. Absolute cross sections and product velocity distributions have been determined for the reactions of (16)O(+) or (18)O(+) ions with CH4 or CD4 from thermal to 5 eV collision energies by using the guided ion beam (GIB) technique. Dissociative photoionization of O2 with vacuum ultraviolet (VUV) synchrotron radiation delivered by the DESIRS beamline at the SOLEIL storage ring and the threshold photoion photoelectron coincidence (TPEPICO) technique are used for the preparation of purely state-selected O(+)((4)S, (2)D, (2)P) ions.