Electric field ionization of highly excited sodiumndatoms

Selective field ionization (SFI) is frequently used to detect atoms in high Rydberg states and to analyze Rydberg population distributions. In order to realize the full potential of this technique, however, a detailed understanding of the behavior of Rydberg atoms during passage from low to ionizing fields is required. The factors influencing this passage are discussed quantitatively and are illustrated by means of detailed SFI data obtained for $\mathrm{Na}34d$ atoms.