K-shell photoionization of CO and N-2: is there a link between the photoelectron angular distribution and the molecular decay dynamics?

We have used COLTRIMS to measure the angular distribution of electrons rele ased from the K-shell of N-2 and the carbon K-shell of CO by absorption of one linear polarized photon. For each ionization event which leads to two c harged fragments we determine the angle of the photoelectron with respect t o the fragment ion momenta. In addition we determine the charge state and e nergy of the molecular fragments. We find a breakdown of the axial recoil a pproximation for CO for kinetic energy releases below 10.2 eV, whereas for N-2 that approximation is found to be valid for all fragment energies. Furt hermore, the photoelectron emission spectrum for N2 is found to be the same for the molecular breakup channels producing N+N+ and N+N++.