Double ionization of ﹩{\mathrm{Ar}}^{0+}﹩ forming ﹩{\mathrm{Ar}}^{2+}﹩. The symbols show the data of Schram (1966, downward-pointing filled triangles), Krishnakumar & Srivastava (1988, filled circles), Syage (1991, open triangles), McCallion et al. (1992a, filled triangles), Straub et al. (1995, filled squares), and Rejoub et al. (2002, filled diamonds). Our fit, described in the text, is illustrated by the solid curve.