Asymmetry parameters for CO2 around the C K and O K ionization edges from the anisotropy of the ion distributions.

Slightly negative {beta} values were found below the C {ital K} edge, rising to a maximum value of 0.9 at the {sigma}{sub {ital u}}{sup *} shape resonance at 312.2 eV. Strongly positive {beta} values were found just below the O {ital K} edge and were assigned to a transition of an O 1{ital s} electron to an {ital s}-type Rydberg orbital coupled with a shape resonance in the {sigma}{sub {ital g}} ionization channel. Two maxima were observed in the {beta} values above the O {ital K} edge and assigned to shape resonances in the {sigma}{sub {ital g}} and {sigma}{sub {ital u}} continuum channels. The lower energy resonance in the {sigma}{sub {ital g}} channel was found at 542.5 eV and the position of the higher energy shape resonance in the {sigma}{sub {ital u}} channel was found to be 560 eV. The importance of using mass-resolved ion spectra to determine the {beta} parameters for molecules which undergo a change in geometry upon excitation of a core electron is highlighted by a comparison of these results with the symmetry-resolved ion yield spectra of CO{sub 2}.