We present a direct comparison between calculated and measured ionization i
n Li and Rb when an initially bound Rydberg electron is stripped from the a
tom by ramping an electric field [0.415 V/(cm ns)]. We describe the method
used to calculate the field dependence of the ionization; the method can be
used to evolve the population from field strengths where three or more n m
anifolds cross to the fields where the electron is stripped from the atom.
The essential feature of the method is the repeated application of the Land
au-Zener approximation for all of the level crossings as the field is rampe
d. We also give a description of the dynamics of Li and Rb in the ramping f
ield. We observe that the Li selective held ionization is sensitive to the
Stark levels within an n manifold, while for Rb only an n dependence is obs
erved.