Zhang Ji-Cai

Elastic Scattering Properties of Ultracold Strontium Atoms

We investigate the elastic scattering properties of strontium atoms at ultracold temperatures. The scattering parameters, such as s-wave scattering lengths, effective ranges and p-wave scattering lengths, are calculated for all stable isotope combinations of Sr atoms by the quantal method and semiclassical method, respectively. Good agreements are obtained. The scattering parameters are very sensitive to small changes of the reduced mass. Due to the repulsive interisotope and intraisotope s-wave scattering length and large elastic cross sections, 84Sr—86Sr mixture is a good candidate to realize Bose—Bose quantum degenerate atomic gases.

Coherent Control of Population Transfer in Li Atoms via Chirped Microwave Pulses

We demonstrate theoretically that Li atoms can be transferred to states of a lower principal quantum number by exposing them to a frequency chirped microwave pulse. The population transfer of Li atoms from the n = 75 state to n = 70 with more than 90% efficiency is achieved by means of the sequential single-photon Δn = –1 transitions. The calculation fully utilizes all of the available orbital angular momentum l states for a given n, and the interference pattern and population evolution dynamics of individual l states are analyzed in detail. Using the time-dependent multilevel approach, we describe the process reasonably well as a sequence of adiabatic rapid passages.

Variable Phase Method Used to Calculate Ultracold Scattering Properties of 7 Li 33 Cs

Elastic scattering properties of singlet and triplet states of7 Li133 Cs at ultralow temperatures are calculated using the constructed potential curves gleaned from high-precision spectroscopy measurement. We show how to reach the scattering length and the number of bound states via the variable phase method. The scattering lengths of the singlet and triplet states of7 Li133 Cs are 50.5a.u. and — 135.7a.u., respectively. We derive two corrections, arising from long range interactions, accurately to at least first order, which provide upper and lower computed bounds to the scattering length. Our results are consistent with the recent experimental data and the theoretical calculation.

Accurate calculation of the elastic scattering properties of ^7Li atoms at ultralow temperatures

The elastic scattering properties for collisions between two 7Li atoms are investigated in the cold and ultracold regimes separately. Based on recent theoretical and experimental results, we present the improved hybrid potentials for the singlet X1∑g+ and triplet a3∑u+ ground states of the Li2. Our calculated values for the scattering lengths a and the effective ranges re are compared with previous ones and found them to be in good agreement. The scattering lengths are 34.6a0 for the singlet state and −27.6a0 for the triplet state. Shape resonances occur in the collisions at low energies. We also calculate the total cross sections and the energy positions of shape resonances for both X1∑g+ and a3∑u+ states.

S-Wave Scattering Properties for Na—K Cold Collisions

Scattering properties of ultracold atoms are sensitive to the interatomic potential. Based on the accurate triplet least-bound state energy, we calculate the triplet s-wave scattering length for 23Na?40K. The scattering length is ?814.1+29?31.3a0 with a0 being the Bohr radius. By using the mass scaling method, those scattering lengths are also obtained for 23Na?41K and 23Na?39K. The degenerate internal state approximation is used to estimate the scattering data of atoms colliding in different spin states.

Scattering properties of the ultracold 133Cs2 triplet state

The elastic scattering properties of ultracold 133Cs2 triplet state are investigated in detail. We construct a potential curve of the 133Cs2 triplet state, based on the latest ab initio molecular potential data and show how the scattering parameters are obtained by using three methods: the Numerov method, the semiclassical method and the variable phase method, where the scattering lengths of the 133Cs2 triplet state, i.e. 301.79a0, 300.67a0 and 310.81a0 are obtained respectively, with a0 being the Bohr radius. We also calculate the effective range and the number of bound states for the 133Cs2 triplet state. Our results are in agreement with the recent experimental data and the theoretical calculations. This confirms that the results of the scattering properties of the ultracold 133Cs2 triplet state, calculated by using these three methods, are reliable.

Elastic Scattering of Ultracold 133Cs and 85Rb Atoms in Triplet State

Elastic scattering properties of the ultracold interaction for the triplet state of 133 Cs and 85 Rb atoms are studied using two kinds of potentials by the same phase . One is the interpolation potential, and another is Lennard-Jones potential (LJ12,6). The radial Schrodinger equation is also solved using two computational methods, the semiclassical method (WKB), and the Numerov method. Our results are found to be in an excellent agreement with the more recent theoretical values. It shows that the two potentials and methods are applicable for studying ultracold collisions between the mixing alkali atoms.