Nondipole effects in the angular distribution of photoelectrons from the C K shell of the CO molecule

Measurements and calculations of a contribution of the nondipole terms in the angular distribution of photoelectrons from the C K shell of randomly oriented CO molecules are reported. In two sets of measurements, the angular distribution in the plane containing the photon polarization and the photon momentum vectors of linearly polarized radiation and the full three-dimensional photoelectron momentum distribution after absorption of circularly polarized light have been measured. Calculations have been performed in the relaxed core Hartree-Fock approximation with a fractional charge. Both theory and experiment show that the nondipole terms are very small in the photon energy region from the ionization threshold of the K shell up to about 70 eV above it.