Fixed-Molecule $1{\mathit{s}\mathit{\sigma }}_{\mathit{g},\mathit{u}}$ Photoelectron Angular Distributions as a Probe of ${\mathit{\sigma }}_{\mathit{g}}^{*}$ and ${\mathit{\sigma }}_{\mathit{u}}^{*}$ Shape Resonances of ${\mathrm{CO}}_2$

Angular distributions of $1s{\sigma }_{g,u}$ photoelectrons from C${\mathrm{O}}_2$ molecules, oriented parallel to the electric vector of incident light, have been measured. The angular distribution patters at ${\sigma }_g^{*}$ and ${\sigma }_u^{*}$ shape resonances are significantly different from those expected in the virtual molecular orbitals concept. The analyses of the patterns have made it clear that the mixing of outgoing photoelectron partial waves and the interference between them are responsible for the observed patterns, unlike ${\mathrm{N}}_2$ photoionization. Calculations based on a quasiatomic model have reproduced the observed patterns fairly well.