Vibrationally resolved partial cross sections and asymmetry parameters for carbon K-shell photoionization of the CO_2 molecule

We have measured the vibrationally resolved partial cross sections \sigma_{v_1^{\prime}} and asymmetry parameters \beta_{v_1^{\prime}} for C K-shell photoionization of the CO2 molecule in the Σu shape resonance region above the C K-shell ionization threshold. The positions of both the maxima of \sigma_{v_1^{\prime}} and the minima of \beta_{v_1^{\prime}} move towards the C K-shell threshold with increasing symmetric stretching vibrational excitation v'1 in the C 1s single-hole state. Calculations employing the relaxed-core Hartree–Fock approach reproduce the observed vibrational effects

Molecular frame photoelectron angular distribution for oxygen 1s photoemission from CO_2 molecules

We have measured photoelectron angular distributions in the molecular frame (MF-PADs) for O 1s photoemission from CO2, using photoelectron-O+–CO+ coincidence momentum imaging. Results for the molecular axis at 0, 45 and 90° to the electric vector of the light are reported. The major features of the MF-PADs are fairly well reproduced by calculations employing a relaxed-core Hartree–Fock approach. Weak asymmetric features are seen through a plane perpendicular to the molecular axis and attributed to symmetry lowering by anti-symmetric stretching motion

Breakdown of the Two-Step Model in K-Shell Photoemission and Subsequent Decay Probed by the Molecular-Frame Photoelectron Angular Distributions of CO_2

We report results of measurements and of Hartree-Fock level calculations of molecular-frame photoelectron angular distributions (MFPADs) for C 1s photoemission from CO2. The agreement between the measured and calculated MFPADs is on average reasonable. The measured MFPADs display a weak but definite asymmetry with respect to the O+ and CO+ fragment ions at certain energies, providing evidence for an overlap of gerade and ungerade final ionic states giving rise to a partial breakdown of the two-step model of core-level photoionization and its subsequent Auger decay

Carbon K-shell photoelectron angular distribution from fixed-in-space CO2 molecules

Measurements of photoelectron angular distributions for carbon K-shell ionization of fixed-in-space CO2 molecules with the molecular axis oriented along, perpendicular and at 45 degrees to the electric vector of the light are reported. The major features of these measured spectra are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. In contrast to the angular distribution for K-shell ionization of N-2, which exhibits a rich structure dominated by the f-wave (l = 3) at the shape resonance, the angular distribution for carbon K-shell photoionization of CO2 is quite unstructured over the entire observed range across the shape resonance