Calculated stark widths of oxygen ion lines

Abstract

Calculations have been performed on the electron impact broadening of isolated lines from singly-ionized and doubly-ionized oxygen emitted from a plasma of electron density 10 17 cm -3 and temperature about 2 eV. These have been compared with results of measurements performed by Platiša, Popović, and Konjević on a plasma produced by a low pressure pulsed arc. Good overall agreement has been obtained for both ionization stages, which we interpret as strong support for a recently derived expression for the effective Gaunt factor in line broadening calculations. This in turn indicates the important role that the curvature of the perturber trajectory plays in the broadening process, and that by proper allowance for this effect, classical path calculations of the isolated ion line widths can be extended to spectra of the multiply-charged ions. Some ambiguity still remains, however, as to the proper method of extrapolation of the effective Gaunt factors below threshold energies in the classical path calculation of the elastic contribution to the broadening. The present comparison appears to indicate that for the higher ionization stages, extrapolation of ḡ as a constant equal to its threshold value, is satisfactory.