| We have studied the C 1s photoionization of acetylene molecules and N 1s photoionization of nitrogen molecules including the core and selected shakeup channels. We calculated the total cross sections as well as partial cross sections for the 1sigma g-1 and 1sigmau -1 channels, which are in good agreement with the high-resolution photoelectron spectra. The use of correlated targets is found to be critical to produce quantitative agreement with experimental values. In both case, a shape resonance is predicted in the 1sigmag -1 channel and an autoionization process via the doubly excited state (1sigmag-1 1pi u-1 1pig -1) is also identified in the multichannel calculation. In the N 1s photoionization of N2, the coupling between channels leading to the 1sigmag-1 and 1sigmau-1 states is found to be much weaker than predicted by random phase approximation method, which agrees well with recent experimental results. The molecular frame photoelectron angular distributions obtained from our calculations are also in agreement with experiments.;Photoionization from ground state of molecular oxygen leading to a number of 1pig-1, 1pi u-1, 3sigmag -1and 2sigmau-1 ion states have been investigated for photon energies up to 50 eV using the multichannel Schwinger configuration interaction method. Quantitative photoionization cross sections and photoelectron asymmetry parameters are obtained for each channels. Substantial interchannel coupling effects have been found in almost every channel. In the photoionization to the 3sigmag -1 channels, a complete failure of the single-channel photoionization description is found in the shape resonance process. In contrast to earlier theoretical studies, we found only one shape resonance in the photoionization to the 3sigmag-1 channels instead of two separated multiplet-specific shape resonances.;The photodetachment from molecular oxygen anion O2 - leading to eleven O2 electronic states have been studied using multichannel Schwinger Hartree-Fock method and multichannel Schwinger configuration interaction method. We found that it is of vital importance to include the electron correlation in these calculations, including the target correlation and interchannel coupling, to obtain even qualitative results. Our calculated total cross sections agree well with the existing experimental data. One Feshbach resonance was found at about 5 eV above the photodetachment threshold. This resonant state has the character of the 1pi u3 1pig 4 configuration. |
