Polarization Dependence of Associative Ionization of Laser-ExcitedNa(3p)P322Atoms

The associative ionization ${\mathrm{Na}}^{*}+{\mathrm{Na}}^{*}\to {{\mathrm{Na}}_2}^{+}+e$, when Na atoms in a single thermal beam are excited by linearly polarized light, was observed. The ion yield increases by a factor of 1.7 when the light polarization vector is rotated from a perpendicular to a parallel direction with respect to the beam. A theoretical analysis shows that the ionization rates $K$ obey the relations $K(\frac{1}{2}, \frac{3}{2})=0\mathrm{}$ and $K(\frac{1}{2}, \frac{1}{2})=1.4K(\frac{3}{2}, \frac{3}{2})$, where the arguments indicate the initial magnetic substates $\left|M_J\right|$ of the two colliding atoms.