Photoproduction ofN22+from threshold to 400 eV

Abstract

We have measured the relative probability for the production of ${\mathrm{N}}_{2}{}^{2+}$ using monochromatized synchrotron radiation in the range of 38 to 400 eV. We find the energy dependence of the ratio ${\mathrm{N}}_{2}{}^{2+}/{\mathrm{N}}_{2}{}^{+}$ to be very similar to that of the ${\mathrm{He}}^{2+}/{\mathrm{He}}^{+}$ ratio, which indicates a similarity in the double-photoionization mechanism. This may allow us to predict the relative dication production for other simple molecules, such as ${\mathrm{O}}_{2}$, without the need to measure an extended photon-energy range. We obtain a threshold for the production of ${\mathrm{N}}_{2}{}^{2+}$ ions of 42.97(10) eV.