The Stark effect of ultra-cold Cs Rydberg atom is investigated in a magneto-optical trap, and the avoided crossing between nS state and (n-4) manifold is observed. The ion spectrum near the avoided crossing is obtained by using state-selective field pulse ionization technique. By changing the intensity of the applied electric field, we find that the relative intensities of two Stark states near the avoided crossing exchange obviously. Furthermore, state transfer from nS Rydberg state to high-l state due to the avoided crossing is also obtained.
The high-l Rydberg Stark states are populated by the state transfer from initial prepared nS Rydberg state via avoided crossings induced by a weak electric-field pulse, and investigated by the state selective field ionization method in a cesium standard magneto-optical trap. The dependences of the transfer rate, given by the ratio of the number of high-l Stark states to all atoms, on the strength and holding time of electric-field pulse are investigated and compared with those with additional ions. The results show that the time evolution of high-l Stark states strongly depends on the electric-field strength, and is affected by the additional ions at relatively weaker field (1.51 V/cm here). The density of Rydberg atoms has a minor effect on the characteristic time of evolution process.
The
l-mixing effect and state-transfer induced by an external electric field pulse in ultracold Rydberg gases are observed with cesium atoms excited to
nS states, and measured with a state selective field ionization technique. High-
l states are populated from the initially excited
nS states due to non-adiabatic transitions through avoided crossings that are formed between the
nS state and the ($n\ensuremath{-}4$) manifold. The population of the product state is investigated as a function of the electric field pulse parameters. The coherent property of the transfer is demonstrated using a 2-pulse sequence and the results are consistent with the theoretical calculations. This
l-mixing phenomenon in the electric field may be used to help forming a molecular potential and create Rydberg molecules.
State-mixing effect of ultracold nS cesium Rydberg atoms in an external electric field is investigated in a magneto-optical trap. Populated high-l Rydberg atoms due to the state-mixing through avoided crossings are measured with a state-selective field ionization technique. The measured transfer rates of high-l states increase with the electric field and get to the maximum at the field of about 3.0 V/cm for 49S1/2 Rydberg state, and show decrease behavior when the electric field increases further. The decrease behavior of the transfer rate is explained with the slower m-mixing effect caused by decreasing dipole–dipole interactions between high-l Rydberg atoms. During the m-mixing process the ultracold plasma is formed by the Penning ionization.
Ultracold cesium n S ( n =60–70) Rydberg atoms are prepared using the two-photon scheme in a magneto-optical trap (MOT). The number of resonant Rydberg atoms is measured by the pulsed field ionization technique, and the dependences of the Rydberg signal on excitation duration and external DC electric field are investigated. The excitation dynamics and blockade effects due to long-range interactions are obtained. The effect of external electric field on Rydberg excitation is also investigated, and the experimental result shows an enhanced blockade with a weak external electric field.
The effects of weak electric fields on resonant energy transfer between
NH3 in the
X 1A1 ground electronic state and Rydberg He atoms in triplet states with principal quantum numbers
n=36--41 have been studied in a crossed-beam apparatus. For these values of
n, electric dipole transitions between the Rydberg states that evolve adiabatically to the $|ns\ensuremath{\rangle}$ and $|np\ensuremath{\rangle}$ states in zero electric field can be tuned into resonance with the ground-state inversion transitions in
NH3 using electric fields, with energy transfer occurring via F\"orster resonance. In the experiments the Rydberg He atoms, traveling in pulsed supersonic beams, were prepared by resonant two-photon excitation from the metastable
1s2s3S1 level and crossed an effusive beam of
NH3 before being detected by state-selective pulsed-electric-field ionization. The resonant-energy-transfer process was identified by monitoring changes in the ionization signal from the $|ns\ensuremath{\rangle}$ and $|np\ensuremath{\rangle}$ Rydberg states for each value of
n. The electric-field dependence of the experimental data is in good agreement with the results of calculations in which the resonant dipole-dipole coupling between the collision partners was accounted for.