In this paper,ultracold atoms and molecules in a dark magneto-optical trap(MOT) are studied via depumping the cesium cold atoms into the dark hyperfine ground state.The collision rate is reduced to 0.45s-1 and the density of the atoms is increased to 5.6×1011cm-3 when the fractional population of the atoms in the bright hyperfine ground state is as low as 0.15.The vibrational spectra of the ultracold cesium molecules are also studied in a standard MOT and in a dark MOT separately.The experimental results are analyzed by using the perturbative quantum approach.
The high precision two-photon excitation measurements for 5S1/2(F87g = 2) to 5D5/2(Fe = 4 to 1) ofRb are performed by using an optical frequency comb.The two counter-propagating femtosecond pulses(5S1/2→5P3/2at 780 nm,and 5P3/2→5D5/2at 776 nm) act on87 Rb vapor,and the Doppler broadened background signal is effectively eliminated.The temperature and power dependences of the two-photon spectrum are studied in this paper.
