Use of numerical optimization algorithms to obtain cross sections from electron swarm data

The use of numerical optimization algorithms has been investigated for estimating the electron momentum transfer and excitation cross sections for atoms and molecules based on measured electron transport, or swarm data. The downhill or creeping simplex method is investigated. This algorithm has been used to obtain the momentum-transfer cross sections ${\mathrm{\sigma }}_{\mathit{m}}$(ɛ) for helium and argon from E/N dependent drift velocities (${\mathit{v}}_{\mathit{d}}$) and characteristic energies (D/μ). In addition, this technique has been used to obtain ${\mathrm{\sigma }}_{\mathit{m}}$(ɛ) and a vibrational excitation cross section for ${\mathrm{CH}}_4$ from measured ${\mathit{v}}_{\mathit{d}}$ and D/μ data. These results serve as examples of what may be possible using these and, perhaps, other optimization algorithms.