K-shell photoionization of CO and N2: 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 released 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 charged fragments we determine the angle of the photoelectron with respect to the fragment ion momenta. In addition we determine the charge state and energy of the molecular fragments. We find a breakdown of the axial recoil approximation 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. Furthermore, the photoelectron emission spectrum for N 2 is found to be the same for the molecular breakup channels producing N + N + and N + N + + .