Manipulating ionization path in a Stark map: Stringent schemes for the   selective field ionization in highly excited Rb Rydberg atoms
  We have developed a quite stringent method in selectivity to ionize the low angular- momentum ($\ell$) states which lie below and above the adjacent manifold in highly excited Rb Rydberg atoms. The method fully exploits the pulsed field-ionization characteristics of the manifold states in high slew-rate regime: Specifically the low $\ell$ state below (above) the adjacent manifold is firstly transferred to the lowest (highest) state in the manifold via the adiabatic transition at the first avoided crossing in low slew-rate regime, and then the atoms are driven to a high electric field for ionization in high slew-rate regime. These extreme states of the manifold are ionized at quite different fields due to the tunneling process, resulting in thus the stringent selectivity. Two manipulation schemes to realize this method actually are demonstrated here experimentally. 
M. Tada, Y. Kishimoto, M. Shibata, K. Kominato, S. Yamada, T.   Haseyama, I. Ogawa, H. Funahashi, K. Yamamoto, S. Matsuki