Low-energy stereodynamics of ion-forming reactions

In this thesis, an experimental study of low-temperature stereodynamics in the reactive scattering of Ne(3P2) + X collisions (X = Ar, Kr, Xe, CO and N2) is presented. The steric effect of Ne(3P2) in these reactions is observed experimentally using a controllable magnetic field. The observations are interpreted using classical and quantum models. This study provides state-selected stereodynamics over a wide range of collision energies from 1000 K down to sub-Kelvin energies using a combination of the merged beam technique and external field manipulation.

The key parameter to characterize the steric effect in these reactions is the branching between different possible reaction channels as a function of magnetic field direction. These branching ratios are obtained for individual states that differ only in Omega, the projection of the neon total angular momentum vector on the inter-particle axis, by using a Monte-Carlo fitting algorithm to fit an analytical expression for the relative importance of the different, state and process-specific, reaction channels to the experimental data. From the comparison of these experimental data, several interesting dynamical phenomena are found, including the reorientation effect and predissociation in atom-molecule collisions, which provides a new way to understand the reaction dynamics at low temperatures.

Finally, we use a combination of an electrostatic hexapole and (2+1) resonance-enhanced multiphoton ionization to produce and characterize an oriented ammonia sample (ND3) using a controllable electric field, which provides a method to study the stereodynamics of Ne(3P2) with oriented polar molecules.