Due to a unit conversion error, the saturation irradiance in this article were wrongly reported. Please note the following corrections to this article: Table 1 lists incorrect saturation irradiances, a corrected table is shown below. Figures 3 and 4 show contain incorrect labels on the horizontal axis and incorrect values for the fit parameters. Corrected versions are shown below. The last paragraph of section "Saturation curves" shows incorrect saturation irradiance values. The corrected numbers are: line 2: 1.42 × 104 W cm −2 , line 5: 1.14 × 106 W cm −2 , line 8: 4.82 × 106 W cm −2. The conclusions section reports a wrong value for the saturation irradiance of the autoionizing transition. The correct value on line 6 is 1.14 × 106 W cm −2. The original article has been revised.