Core-excitation in molecules: Formation of cations and anions

The formation of positively and negatively charged ions is reported for core-excited carbon dioxide (CO2) and nitrous oxide (N2O) in the soft X-ray regime using monochromatized synchrotron radiation. These molecules are investigated in the energy regimes of the C(1s)- and N(1s)-absorption edges. It is found that the shape of photoion yield spectra of mass selected cations depends strongly on the dominating fragmentation mechanism which leads to the product ion. Anion formation is identified as a primary process in the core ionization regime. Both CO2 and N2O decay exclusively into the anion channel O-, predominantly upon 1s-->pi*-excitation. The formation mechanisms of cations and anions in core-excited molecules are discussed.