Angular distributions of photoelectrons ejected from fixed-in-space molecules of C3v symmetry group

The angular distributions of photoelectrons from fixed-in-space molecules of C3v symmetry group are studied for the particular case when the light beam is incoming parallel to the C3 rotational axis of the molecule. The consideration is based on the expansion of photoelectron wave functions in symmetry-adapted spherical harmonics. The analytical equations for the angular distributions of photoelectrons ejected by linearly polarized, circularly polarized, and unpolarized light have been derived. The threefold symmetry of the target reveals itself most clearly for circularly polarized and unpolarized light when the dependence on the azimuthal angle is studied for a fixed polar angle. For linearly polarized light the photoelectron angular distributions have a more complicated dependence on the azimuthal angle. On the other hand, with linearly polarized light one can easily distinguish between the a1 and a2 initial states by observing the zeroes of photoelectron intensities in the symmetry plane ejected by light linearly polarized either in the symmetry plane or perpendicular to the symmetry plane. The numerical examples presented in the paper demonstrate the general properties of the angular distributions as well as properties of the circular and linear dichroism in the angular distribution.