MICROWAVE IONIZATION RATES OF NA STARK STATES

Near threshold the microwave ionization rates of Na m=0,1 Rydberg states within a Stark manifold n show a strong dependence on the location of the state within the manifold. In particular, the rate-limiting step for ionization of states with the smallest Stark shifts (kn) is different from the field-limited step of making the nn+1 transitions at threshold fields FT1/3n5 (a.u.). This variation in the ionization rates as a function of manifold location or Stark shift may be understood in terms of the variation in the transition probability to the bluest Stark states from the other members of the manifold. © 1990 The American Physical Society.