Asymmetry in the ionic fragmentation of N2O photoexcited around the N and O K edges

Abstract

Asymmetry parameters (β) for the fragment ions of N₂O following excitation or ionization of the N and O K shell electrons have been determined from photoelectron–photoion coincidence (PEPICO) and photoion–photoion coincidence (PIPICO) spectra measured using monochromatized synchrotron radiation and a rotatable time‐of‐flight mass spectrometer. Profiles of the β parameters from the N⁺ ions with low kinetic energies (K.E. K edges. β parameter profiles for the O⁺ ions with contributions from N⁺ ions with K.E. ≳4.5 eV and N₂⁺ ions overlapped with NO⁺ ions show structure with negative values at the π* resonances below the N K‐edges and positive values at the unresolved Rydberg resonances below the terminal N K edge and O K edge and at the shape resonance above the N K edges. β parameters from the N⁺–NO⁺ and N₂⁺–O⁺ PIPICO signals were found to be considerably more anisotropic than the corresponding values from the PEPICO signals at the π* resonances below the N K edges and the shape resonance above the ionization edges. β parameters from both the PEPICO and PIPICO signals were close to zero at the π* resonance below the O K edge. The higher degree of anisotropy of ionic fragmentation observed in the PIPICO signals highlights the importance of measuring the fragmentation spectra of polyatomic molecules in coincidence in order to obtain accurate β parameters.