The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number ｜m｜ shift upward a lot, and those with a large ｜m｜ shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with ｜m｜=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.
This paper reports that ultracold atoms are populated into different nS and nD Rydberg states （n=25-52） by two-photon excitation. The ionization spectrum of an ultracold Rydberg atom is acquired in a cesium magneto-optical trap by using the method of pulse field ionization. This denotes nS and nD states in the ionization spectrum and fits the data of energy levels of different Rydberg states to obtain quantum defects of nS and nD states.
In this paper, an ultra-high resolution photoassociation spectroscopy study on photoassociation of cesium atoms is reported. The cold cesium gas in the mag-neto-optical trap is illuminated by a photoassociation laser with red-tuning as large as 40 cm?1 below the 6S1/2 + 6P3/2 dissociation limit, and the photoassociation to the excited state ultracold molecule is detected. High signal-to-noise ratio is obtained by using the lock-in detection of the fluorescence from the modulated cold Cs at-oms. The 0g?, 1g and 0u+ long-range states which correspond to 6S1/2 + 6P3/2 dissocia-tion limit are present in the photoassociation spectrum. The effective coefficients of leading long-range interactions and the corresponding vibrational quantum num-ber are obtained using LeRoy-Bernstein Law. It is found that photoassociation process creates rotating molecules and the high J value is a hint that higher partial waves participate in the PA process in the presence of trapping laser.
WANG LiRongMA JieJI WeiBangWANG GuiPingXIAO LianTuanJIA SuoTang
Signals of ultracold plasma are observed by two-photon ionization of laser-cooled caesium atoms in a magnetooptical trap. Recombination of ions and electrons into Rydberg atoms during the expansion of ultracold plasma is investigated by using state-selective field ionization spectroscopy. The dependences of recombination on initial electron temperature （1 70 K） and initial ion density （-10^10 cm-3） are investigated. The measured dependence on initial ion density is N^1.547±0.004 at a delay time of 5μs. The recombination rate rapidly declines as initial electron temperature increases when delay time is increased. The distributions of Rydberg atoms on different values of principal quantum number n, i.e. n = 30-60, at an initial electron temperature of 3.3 K are also investigated. The main experimental results are approximately explained by the three-body recombination theory.
