Gao-Ren Wang

Creation of ultracold Cs2 molecules via two-step photoassociation with Gaussian and chirped pulses

An efficient two-step photoassociation (PA) scheme is used to produce ultracold Cs2 molecules in the excited electronic state. By using the compression effect of the wavepacket in the ground electronic state induced by the Gaussian pulse L1, the PA efficiency PL of forming ultracold molecules in the excited electronic state with binding energies greater than 3.0 cm−1 steered by the pulse L2 can be efficiently enhanced. The influences of temporal width, electric field amplitude and chirp rate on the PA dynamics are analyzed. Moreover, the total PA efficiency is also estimated when the thermal distribution is taken into account.

The radio frequency field modulation of magnetically induced heteronuclear Feshbach resonance

The heteronuclear atomic collision in the presence of a radio frequency (RF) electric field and a dc magnetic field is investigated theoretically by using the asymptotic bound state model. A RF field can be used to modify Feshbach resonance by choosing suitable intensity and frequency. The control mechanism is based on the interaction of the RF electric field with the instantaneous dipole moment of the collision atomic pair. We find an interesting phenomenon: the character exchange of the Feshbach resonances and resonance interference modulated by the RF field takes place in the ultracold collision of 6Li and 40K. This resonance interference may be used to modify the interactions in ultracold quantum gases.

Quantum reflection by the Casimir–Polder potential: a three-parameter model

We investigate the quantum reflection governed by the Casimir?Polder potential which scales as ?1/r3 at short separation and as ?1/r4 at long separation. Using the available analytical solutions for the ?1/r4 potential and quantum defect theory, we develop a three-parameter model for quantum reflection. The three parameters characterizing the potential are essentially constant near the threshold. The application scope of the model is examined. For a potential dominated by the ?1/r4 behaviour, which is the case in many realistic atom?surface systems, our model gives accurate results over the energy range in which the quantum reflection is significant. Moreover, this parameterized model allows one to fit the experimental data efficiently.