Electron impact vibrational excitation in plasmas

The vibrational excitation of molecules by electrons in diffuse plasma, such as those found in cometary coma or used in industrial etching, is a key but poorly understood process. Excited vibrational states can either emit photons giving rise to tell-tale observable signature emissions or be a stepping-stone to further processes such as dissociation via further electron impacts.

Vibrational excitation cross sections are hard to measure even for excitations from the vibrational ground state and essentially unmeasured for excited states. The proposal is to study vibrational excitation for key molecules naturally (such as water) and etching plasmas (such as NF, NF2 and NF3). This study will be performed by developing the UK Molecular R-matrix code (UKRMol) which were developed under various EPSRC grants and forms the basis of the Quantemol-N expert system distributed by Quantemol Ltd. Both these codes have been used to study electron collisional excitations of importance both for pure physics investigations (eg electron impact rotational excitation) and plasma physics (eg electron impact dissociation and ionisation). Thus far vibrational excitation has only been studied for the special case of resonant excitation of diatomic molecules using a standalone code and a non-extendable procedure.