No abstract

Three and four generalized Lorentzians in two variables have been obtained to approximate the Voigt function by using the asymptotical Padé method. The accuracy has been greatly improved with respect to the one and two generalized Lorentzian approximations reported in a previous paper. Furthermore, the four Lorentzian function is always positive for all values of the normalized collision width and line separation. This approximation gives an accuracy for most of the values of better than 0.0001, and in the worst region the absolute error is ~0.001. In the limits of low and high pressure adequate limit functions are obtained. A four generalized Lorentzian gives a reliable and easily calculable approximation to the Voigt function for most of the experimental needs.

The object of the work reported in this paper was to find a simple and easy to calculate approximation to the Voigt function using the Padé method. To do this we calculated the multipole approximation to the complex function as the error function or as the plasma dispersion function. This generalized Lorentzian approximation can be used instead of the exact function in experiments that do not require great accuracy.

The M o l d behaviour of eledmn impact ionization of argon atoms and nitrogen molecules is investigated state selectively using the vanstational energy sptromeby (ms) method. A power law of the form # ( E d ) a (Ee, -E d " can be fitted to the measured ionization fnnctions. For double ionization of Ar and Nz we found good agreement with the theoretical predictions based on the Wannier theory for the electron triple escape process. Coefficients for the triple ionization of Ar are closer to those predicted by a swistical model.

A velocity analyzer with adjustable interelectrodic distances is described here. Several experiments have been performed in a double plasma machine with this analyzer of variable geometry in order to investigate the effects of the discontinuous structure of the grids. The measured displacements of the characteristic curve for different interelectrodic distances show excellent agreement with the theoretical predictions due to the depletion of the discriminating potential in the holes of the grid, as is shown in our recent theoretical analysis using a Schwarz–Christoffel transformation. The influence of the grid structure on the temperature determined from the characteristic curve is also investigated and the correlation experiment theory is qualitatively correct.