K-shell photoexcitation of solid ${\mathrm{N}}_2$, CO, NO, ${\mathrm{O}}_2$, and ${\mathrm{N}}_2$O

Excitation spectra of photon-stimulated ion desorption (PSID) and total photoelectron yield at C K, N K, and O K absorption edges are reported and compared with appropriate published spectra of the gas phase. Analyses of the PSID spectra based on the three-step Knotek-Feibelman process result in identification of Auger-generated ionic dissociative states which are consistent with published results of gas-phase electron-energy-loss studies. The Auger-generated ionic molecular dissociative state is shown to involve two valence-level holes and one excited-state electron in several cases. The most prominent feature in all solid-phase spectra is identified with the photogenerated 1s→${\pi }^{\mathrm{*}}$ molecular excitation which is observed at all three K-absorption edges in both electron and ion excitation spectra. This resonance excitation is a single peak in ${\mathrm{N}}_2$, CO, and ${\mathrm{O}}_2$ solids, but is split in solid ${\mathrm{N}}_2$O by 3.9 eV and in solid NO by 1.3 eV. In ${\mathrm{N}}_2$O the splitting is due to the inequivalence of the two nitrogen atoms, while in NO it is due to intermolecular charge transfer in the NO dimers, of which the solid is composed. The 1s→${\pi }^{\mathrm{*}}$ excitation energies are found to be smaller in solid ${\mathrm{N}}_2$ and ${\mathrm{N}}_2$O by 0.4 to 0.7 eV, compared to the gases. Spectrally dependent ionic fragmentation patterns are presented and compared with available data on the gas-phase photodissociative ionization.