Electronic-state interference in the C 1s excitation and decay of methyl chloride studied by angularly resolved Auger spectroscopy

Resonant Auger (RA) decay spectra of carbon 1s excited CH3Cl molecules are recorded with angular resolution using linearly polarized synchrotron radiation. The selected photon energies corresponding to the C 1s→8a1 core to lowest unoccupied molecular orbital and C 1s→4sa1, 4pe, and 4pa1 core to Rydberg excitations of methyl chloride are used and electrons in the binding energy range of 11-37 eV are detected. The vibrationally unresolved RA electron angular distributions, recorded for participator Auger transitions populating the X, A, B, and C states of the CH3Cl+ ion, exhibit strong variations across the selected electronic resonances. These observations are interpreted with the help of ab initio electronic structure and dynamics calculations, which account for electronic-state interference between the direct and different resonant ionization pathways. For spectator transitions, the theory predicts almost isotropic angular distributions with moderate changes of β parameters around zero, which is in agreement with the experimental observations