Photoelectron spin polarization in autoionization of NO molecules preparedby jet cooling

The photoionization of NO molecules is studied using angle- and spin-reserv ed photoelectron spectroscopy with circularly polarized synchrotron radiati on. The spin-orbit splitting is resolved by preparing only the X (2)Pi(1/2) component of the ground state in a helium-seeded supersonic expansion. A p ronounced spin polarization in the angular distribution is found for the co ld beam when the strong autoionization resonance at 13.82 eV photon energy is excited. The polarization parameters A, xi and alpha are determined for the nu = 2 and 3 vibrational levels of the NO+ X (1)Sigma(+) final ionic st ate. The results lead to the conclusion that resonances with (2)Sigma(+) an d (2)Delta symmetry contribute with similar intensity. The dominant contrib utions to the dipole transition matrix elements of the emitted electron wav es can be derived approximately.