Obtaining electron attachment cross sections by means of linear inversion of swarm parameters

We investigate electron attachment to strongly attaching gases as a function of the electron energy. The total electron attachment cross section of this electronegative sample gas is determined from the effective ionization rate constant.eff/ N measured in a swarm experiment using the buffer gases N2 and CO2 with minor proportions (. 0.8%) of the sample gas SF6, and C3F8 respectively. The measured rate constants.eff/ N for varying reduced electric field strengths E/ N are unfolded from the electron energy distribution of the buffer gases. Different unfolding routines for so- called ill- posed problems are tested to find robust solutions for the attachment cross section. Finally, we propose Tikhonov regularization, which is a well defined algorithm for discrete linear inversion problems, as most efficient. Our method gives rise to an approximate and clearly defined solution for the attachment cross section, and it is described in detail.