Field ionization processes of highly excited Rydberg states under a rotating electric field

将 多田

真司 植松

Satoru Yamada

Ionization property of highly excited Rydberg states of rubidium 85 under a rotating electric field has been investigated experimentally and theoretically.In the experiment, manifold states whose principal quantum number 112 :s; n :s; 137 have been directly populated by a two-step

康弘 岸本

Shigeru Yamada, H. Funahashi, M. Shibata +7 more

Field ionization of high Rydberg manifold states $(n=112\text{--}137)$ of rubidium-85 under a rotating electric field has been investigated experimentally and theoretically. Applying a rapidly reversed electric field with a small static perpendicular field to rotate the total electric field around zero, we have observed substantial increase of the fraction of the tunneling field-ionization process and a profound broadening of its ionization peak over a wide range of field strengths with increasing transverse electric field. The observed tunneling field-ionization fraction is almost independent of the slew rate of the applied electric field, and also on the principal quantum number $n$ over the range investigated. To compare with these experimental results, theoretical calculations have been performed with a successive two-step regime. As the first step we calculated the redistributions of magnetic quantum number ${m}_{\ensuremath{\ell}}$ and parabolic quantum number ${n}_{1}\ensuremath{-}{n}_{2}$ of the states under the rotating electric field. Then the following time evolution of the manifold states with $\ensuremath{\mid}{m}_{\ensuremath{\ell}}\ensuremath{\mid}\ensuremath{\leqslant}3$ was traced on the Stark map in a coherent as well as an incoherent model. The calculated results are generally in good agreement with the experimental ones. The increase of the tunneling field-ionization fraction under a rotating electric field plays an essential role in achieving the high efficiency in the recently proposed selective-field-ionization scheme for high Rydberg atoms.

Jing Zhang, Shen Li, Dai Chang-Jian

The field ionization process of the Eu 4f 7 6s n p Rydberg states, converging to the first ionization limit, 4f 7 6s 9 S 4 , is systematically investigated. The spectra of the Eu 4f 7 6s n p Rydberg states are populated with three-step laser excitation, and detected by electric field ionization (EFI) method. Two different kinds of the EFI pulses are applied after laser excitation to observe the possible impacts on the EFI process. The exact EFI ionization thresholds for the 4f 7 6s n p Rydberg states can be determined by observing the corresponding EFI spectra. In particular, some structures above the EFI threshold are found in the EFI spectra, which may be interpreted as the effect from black body radiation (BBR). Finally, the scaling law of the EFI threshold for the Eu 4f 7 6s n p Rydberg states with the effective quantum number is built.