Measurements of angular distribution for photoionization of mercury into the 5d9 2D5/2 ionic state over the energy range from 15 eV to 17 eV

Differential cross sections for photoionization into the 5d(9)6s(2) D-2(5/2) ionic state of mercury have been obtained over the photon energy range from 15 eV to 17 eV. By measuring the photoelectron emission at the angles of 0 and 90 with respect to the major axis of the polarization ellipse the variation of the asymmetry beta-parameter for the D-2(5/2) ionic state of mercury has been determined as a continuous function of photon energy over the above range. This energy range contains three series of autoionizing states converging to the D-2(3/2) ionization limit. The measurements have been performed using the 5 m McPherson normal incidence monochromator at the Daresbury Synchrotron Radiation Source with a photon energy spread of typically 3 m\eV.