Polarization and velocity dependence of associative ionization in Na(3p)+Na(3p) collisions

We have excited Na atoms of two counterrunning thermal beams by means of linearly polarized laser light and have investigated associative ionization processes. To this end we measured the total ionization signal as a function of the angle ? between light polarization and the relative collision velocity. Velocities of the excited atoms were selected by exploiting the Doppler effect. We found an increasing polarization dependence at increasing collision velocities. At all velocities the preparation of the collision partners in the |M _j |=1/2 sublevel of the Na² P _3/2 state is most efficient in producing ionization.