We report the observation of unusual doubly excited states of barium: Ba (5dj, 21c). One of the valence electrons of Ba is prepared in an oriented circular Rydberg state (n = 21, l = m = 20, denoted 21c) by the adiabatic crossed-fields method. The other electron is excited to a 6pj state which decays radiatively to a 5dj metastable level. The measured autoionization lifetime of Ba (5d5/2, 21c) is T ~ 1 μ s , whereas for Ba (5d3/2, 21c), τ is estimated to be longer than 400 μs. This very large difference of lifetimes between the fine-structure states of the inner electron has been analysed.
Using the adiabatic crossed-field method we have prepared for the first time doubly excited barium atoms with one valence electron in an oriented circular Rydberg state (n=21, l=m=20, denoted 21c) and the other electron in a
6pj state. In a fraction of these atoms the inner electron decays radiatively to a ${5\mathrm{d}}_{\mathrm{j}\ensuremath{'}}$ metastable level. The obtained circular-metastable doubly excited atoms are very stable. For the (${5\mathrm{d}}_{3/2>}$21c) state the autoionization lifetime \ensuremath{\tau} is longer than 400 \ensuremath{\mu}s; for the (${5\mathrm{d}}_{5/2}$21c) state, \ensuremath{\tau}=1\ifmmode\pm\else\textpm\fi{}0.2 \ensuremath{\mu}s. the specific role of the 5d electron is demonstrated. \textcopyright{} 1990 The American Physical Society
Circular Rydberg states with
n=70 have been prepared in helium using a modified version of the crossed-fields method. This approach to the preparation of high-
n circular Rydberg states overcomes limitations of the standard crossed-fields method which arise at this, and higher, values of
n. The experiments were performed with atoms traveling in pulsed supersonic beams that were initially laser photoexcited from the metastable
1s2s3S1 level to the
1s73s3S1 level by resonance-enhanced two-color two-photon excitation in a magnetic field of 16.154 G. These excited atoms were then polarized using a perpendicular electric field of 0.844 V/cm, and transferred by a pulse of microwave radiation to the state that, when adiabatically depolarized, evolves into the
n=70 circular state in zero electric field. The excited atoms were detected by state-selective electric field ionization. Each step of the circular state preparation process was validated by comparison with the calculated atomic energy-level structure in the perpendicular electric and magnetic fields used. Of the atoms initially excited to the
1s73s3S1 level, $\ensuremath{\sim}80%$ were transferred to the
n=70 circular state. At these high values of $n, \mathrm{\ensuremath{\Delta}}n=1$ circular-to-circular Rydberg state transitions occur at frequencies below 20 GHz. Consequently, atoms in these states, and the circular state preparation process presented here, are well suited to hybrid cavity QED experiments with Rydberg atoms and superconducting microwave circuits.
With pulsed and cw laser radiation we investigated doubly‐excited, autoionizing states of Ba, 4fnf series were excited from metastable 5d2 states using two pulsed dye lasers and 5dnf intermediate states. To explain the data on high‐lying states knowledge of the wave functions of the intermediate states and their perturbers is prerequisite. In preparation of experiments on double circular states such as 4f2, 4f5g, 5g2 etc., we studied the 5d5g multiplet, excited with two pulsed lasers from 6s5d metastable states. Furthermore we present results of a study of 6pnl states with large l, excited with two narrowband cw lasers. 6snl states were populated in a beam from metastable 5d2 states in the presence of an electric field. The atomic motion was used to reduce the field adiabatically to zero before applying the second excitation step (Stark switching). The results show that further excitation to 7dnl and even Nfnl states is feasible, giving possibilities to study the three‐body Coulomb problem with cw laser resolution.
We report the first observation of hyperfine structure and isotope shift in autoionizing states. This structure was investigated in the $5{d}_{\frac{3}{2}}\mathrm{nf} J=4,5(n=36\ensuremath{-}40)$ barium Rydberg series, excited from the recently localized metastable $5{d}^{2}^{1}G_{4}$ level. An isotope-selective detection method was used in a cw laser spectroscopic experiment on a collimated atomic beam. The experimental data provide valuable additional information for the analyses of these doubly excited series.