Temperature of the Remaining Cold Atoms after Two-Step Photoionization in an 87Rb Vapor Cell Magneto-Optical Trap
RUAN Ya-Ping1, JIA Feng-Dong1, LIU Long-Wei1, SUN Zhen1, HUANG Wei2, XUE Ping3, XU Xiang-Yuan3,4, DAI Xing-Can3, ZHONG Zhi-Ping1**
1School of Physics, University of Chinese Academy of Sciences, PO Box 4588, Beijing 100049 2Laboratory of Quantum Engineering and Quantum Materials, SPTE, South China Normal University, Guangzhou 510006 3State Key Laboratory for Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084 4Department of Physics, Capital Normal University, Beijing 100037
Abstract：The temperature of the remaining cold 87Rb atoms confined in a vapor cell magneto-optical trap after two-step photoionization has been measured. In the two-step photoionization process, the first excitation laser is served by the cooling laser and the second excitation laser is served by a continuous semiconductor laser with a wavelength of 450 nm. The results show that the temperature of the remaining cold atoms decreases as the intensity of the second excitation laser increases. Moreover, the relationship between the temperature T and number N of the remaining cold atoms generally follows a power law, while it deviates from the well-known T∝N1/3 and the power factor is smaller than 1/3. We propose that ion-atom collisions occurring during a photoionization process strongly influence the temperature scaling law in an optically dense magneto-optical trap in the presence of an ionization laser. In addition, the forced evaporative cooling due to the combined effect of the detuning of the first excitation laser and the two-step photoionization plays a role in cooling the remaining cold atoms and results in the dependence of the power factor on the detuning of the first excitation laser.
2014, Vol. 31 
