Chemistry, Light and Dynamics Seminar

Brianna Heazlewood: New methods for studying ion-neutral reactions at low temperatures

Abstract: In spite of their real-world importance, very few experimental methods can be applied to the precise study of gas-phase reaction systems involving ions and radicals. This is primarily due to the challenges associated with generating a pure beam of gas-phase radicals with tuneable properties. In this seminar, I will present our approach to generating beams of velocity- and state-selected radicals. We are in the process of combining the radical beam source with a cryogenic ion trap, for the study of ion-radical reactions under cold and controlled conditions. Reactions will take place within Coulomb crystals, enabling us to monitor processes with exceptional sensitivity (down to the single-ion level). Recent work on some 'simple' ion-neutral reactions will be discussed, revealing the advantages of studying reaction processes within Coulomb crystals.    

Bridgette Cooper:  Title: Electron-molecular scattering with Quantemol Electron Collisions (QEC)

Abstract: Electron-molecular collisions are of great importance to plasma physics and its applications, particularly for the semi-conductor industry. In this talk I will present the Quantemol Electron Collisions (QEC) [1] software. QEC is a graphical user interface to support quantum mechanical simulations of these fundamental scattering processes. QEC provides robust and reliable cross-section calculations by interfacing both Molpro [2] quantum chemical package for accurate molecular targets and the UKRMOL+ [3] packages for state of the art scattering calculations. Through this software it is possible to calculate observables from both elastic and a wide variety of inelastic scattering channels.

The focus of the talk will be recent enhancements to this software particular the ability to calculate ionisation cross sections for molecules containing heavy elements (>40 atomic mass units) essential for plasma fusion devices and mass spectrometry studies. This is achieved through the use of effective core potentials for the description of the molecule target, and the Binary Encounter Bethe approximation to the ionisation cross section [4]. Upon ionisation a molecule often fragments, however it is harder to predict the fragmentation channels, and relative abundance of each fragment species. I will discuss recent work [5] in collaboration with the Price group at UCL that has investigate how we can use ionisation cross sections from QEC with experimental data [6], mass spectrometry data or ab initio calculation to predict fragment ionisation cross sections.