Cross sections and transport properties for electrons in Zn vapour

Full text: It has been recently suggested that zinc could be an attractive replacement for mercury in making high-pressure gas dis- charge lamps more environmentally friendly. Modelling the operation of these lamps requires knowledge of the electrical conductivity of the buffer gas, which is largely determined by the electron mobility coefficient. Unfortunately neither experimental cross sections nor mobility coefficients for zinc are readily available. It is highly unlikely that the experimental swarm technique used to determine such properties for mercury vapour could be repeated for zinc vapour due to the high vapour temperatures required for such measurements. Neither are there any single-scattering beam experiment data available for zinc vapour. Hence, at this stage the only recourse appears to be the use of theoretical electron impact cross-sections in a Boltzmann equation analysis to theoretically determine transport properties of electrons in zinc vapour. This presentation will report on 1. ab initio calculations of the (e,Zn) elastic momentum transfer and inelastic excitation cross sections; and 2. electron impact excitation rate coefficients corresponding to VUV emission, transport coefficients (including electron mobility, and electron diffusion coefficients) obtained from multi-term solution of Boltzmann's equation using this cross section and theoretical excitation cross-sections over a range of reduced electric fields E/N (where N is the gas number density) and gas temperatures likely to be encountered in operating circumstances of such discharge lamps