In comparing evaporative cooling to Bose-Einstein Condensation in the F=2, mf= 2 and F=l, mf= -1 states of 87Rb we observe fewer condensate F=2 atoms, in contrast with a simple model.

Quantum Electronics and Laser Science ConferenceMay 18, 19970 citations

Production of87Rb Bose—Einstein condensates in a hybrid trap

Yafan Duan, Bo-Nan Jiang, Jian-Fang Sun +3 more

Chinese Physics BMay 1, 20134 citations

Chinese Optics Letters

Evaporative cooling rubidium atoms with microwave radiation

熊德智 Dezhi Xiong, 王鹏军 Pengjun Wang, 陈海霞 Haixia Chen, 张靖 Jing Zhang

Published Jan 1, 2010• 4 citations

Publisher

Abstract

DOI: 10.3788/m0000520100804.0351

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Dezhi Xiong, Pengjun Wang, Haixia Chen +1 more

We report the experimental achievement of 87 Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency (RF) induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the 87 Rb atoms to transit from the ground-state hyperfine state |F = 2, mF = 2 to |F = 1, mF = 1 .Compared with RF-induced evaporation, 87 Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the |F = 1, mF = 1 state being pumped back into the trapping |F = 2, mF = 1 state.We report the experimental achievement of 87 Rb Bose-Einstein condensation in a magnetic trap with microwave and radio frequency (RF) induced evaporation.Evaporative cooling is realized by using 6.8 GHz microwave radiation driving the 87 Rb atoms to transit from the ground-state hyperfine state |F = 2, mF = 2 to |F = 1, mF = 1 .Compared with RF-induced evaporation, 87 Rb atoms are hardly to achieve pure condensate by microwave evaporation cooling due to the effect of atoms in the |F = 1, mF = 1 state being pumped back into the trapping |F = 2, mF = 1 state.

Chinese Optics LettersJan 1, 20105 citations

Experimental investigation of evaporative cooling mixture of bosonic 87 Rb and fermionic 40 K atoms with microwave and radio frequency radiation

Pengjun Wang, Dezhi Xiong, Zhengkun Fu +1 more

We investigate sympathetic cooling fermions 40 K by evaporatively cooling bosonic 87 Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic atoms is prepared in their polarized spin states | F = 9/2, m F = 9/2〉 for 40 K and | F = 2, m F = 2〉 for 87 Rb, which is trapped in Quadrupole—Ioffe—Configuration trap. Comparing microwave with radio frequency evaporatively cooling bosonic 87 Rb atoms with sympathetically cooling Fermi gas 40 K, we find that the presence of rubidium atoms in the |2, 1〉 Zeeman states, which are generated in the evaporative process, gives rise to a significant loss of 40 K due to inelastic collisions. Thus, the rubidium atoms populated in the |2, 1〉 Zeeman states should be removed in order to effectively perform sympathetically cooling 40 K with the evaporatively cooled 87 Rb atoms.We investigate sympathetic cooling fermions 40 K by evaporatively cooling bosonic 87 Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic atoms is prepared in their polarized spin states | F = 9/2, m F = 9/2〉 for 40 K and | F = 2, m F = 2〉 for 87 Rb, which is trapped in Quadrupole—Ioffe—Configuration trap. Comparing microwave with radio frequency evaporatively cooling bosonic 87 Rb atoms with sympathetically cooling Fermi gas 40 K, we find that the presence of rubidium atoms in the |2, 1〉 Zeeman states, which are generated in the evaporative process, gives rise to a significant loss of 40 K due to inelastic collisions. Thus, the rubidium atoms populated in the |2, 1〉 Zeeman states should be removed in order to effectively perform sympathetically cooling 40 K with the evaporatively cooled 87 Rb atoms.

Chinese Physics BJan 1, 20115 citations

Interrupted evaporative cooling of 87Rb atoms trapped in a high magnetic field

Bruno Desruelle, Vincent Boyer, Stuart G. Murdoch +4 more

Radio-frequency-induced evaporative cooling of ${}^{87}\mathrm{Rb}$ atoms in the $F=2,$ $m=2$ ground state in a magnetic trap with a high bias field is found to be hampered, and eventually interrupted, by the presence of nonlinear Zeeman shifts. An experiment studying evaporation at a fixed adjustable rf frequency was used to illustrate this effect. These nonlinear shifts prevent us from reaching quantum degeneracy in the $F=2,$ $m=2$ ground state; however, evaporation in the $F=1,$ $m=\ensuremath{-}1$ ground state is not adversely affected, and we can produce a Bose-Einstein condensate (BEC). Our analysis shows that this effect can play a role in many BEC experiments.Radio-frequency-induced evaporative cooling of ${}^{87}\mathrm{Rb}$ atoms in the $F=2,$ $m=2$ ground state in a magnetic trap with a high bias field is found to be hampered, and eventually interrupted, by the presence of nonlinear Zeeman shifts. An experiment studying evaporation at a fixed adjustable rf frequency was used to illustrate this effect. These nonlinear shifts prevent us from reaching quantum degeneracy in the $F=2,$ $m=2$ ground state; however, evaporation in the $F=1,$ $m=\ensuremath{-}1$ ground state is not adversely affected, and we can produce a Bose-Einstein condensate (BEC). Our analysis shows that this effect can play a role in many BEC experiments.

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Fast production of 87Rb Bose-Einstein condensates

陈良超 CHEN Liang-chao, Zengming Meng, Pengjun Wang

A rapid atomic beam of rubidium (87Rb) is produced by two-dimensional magneto-optical trap (2D MOT), and then trapped by three-dimensional magneto-optical trap (3D MOT) with high vacuum for further cooling. After a process of optical molasses cooling, atoms are reloaded into a magnetic trap, where radio frequency (RF) evaporation cooling is implemented. The precooled atoms in the magnetic trap are then transferred into a far detuning optical dipole trap, where Bose-Einstein condensate (BEC) appears by further evaporation cooling. The 3D MOT is loaded to its maximum within 25 s and then BEC is prepared in 16 s. Due to the linear intensity of magnetic trap, the frequency can be scanned fast in the RF evaporation cooling process. In our experiment, the frequency scans from 39 MHz to 15 MHz in 6 s and then scans to 2 MHz in 5 s. The number of atoms in 3D MOT is about 11010, and there are 5105 atoms in the BEC after a succession of cooling processes. To optimize the performances of 2D MOT, a special light path is constructed. And prisms with high reflectivity are used to reduce the imbalance between opposite propagating cooling +beams. Furthermore, quarter-wave plates are used to keep the polarization state of the cooling beam when reflected by prisms or mirrors. The atoms are cooled to a temperature about 15 K in the magnetic trap by RF evaporation. In such a low temperature, the loss of magnetic trap (Majorana loss) will prevent the atoms from reaching a high density, and the atoms cannot be cooled further. To reduce the loss rate of the magnetic trap, the far blue detuning light (532 nm, 18 W) is added to plug the zero point of the magnetic trap. In the optically plugged magnetic trap, atoms with high density are cooled down enough, which gives a good start for the loading of optical dipole trap.A rapid atomic beam of rubidium (87Rb) is produced by two-dimensional magneto-optical trap (2D MOT), and then trapped by three-dimensional magneto-optical trap (3D MOT) with high vacuum for further cooling. After a process of optical molasses cooling, atoms are reloaded into a magnetic trap, where radio frequency (RF) evaporation cooling is implemented. The precooled atoms in the magnetic trap are then transferred into a far detuning optical dipole trap, where Bose-Einstein condensate (BEC) appears by further evaporation cooling. The 3D MOT is loaded to its maximum within 25 s and then BEC is prepared in 16 s. Due to the linear intensity of magnetic trap, the frequency can be scanned fast in the RF evaporation cooling process. In our experiment, the frequency scans from 39 MHz to 15 MHz in 6 s and then scans to 2 MHz in 5 s. The number of atoms in 3D MOT is about 11010, and there are 5105 atoms in the BEC after a succession of cooling processes. To optimize the performances of 2D MOT, a special light path is constructed. And prisms with high reflectivity are used to reduce the imbalance between opposite propagating cooling +beams. Furthermore, quarter-wave plates are used to keep the polarization state of the cooling beam when reflected by prisms or mirrors. The atoms are cooled to a temperature about 15 K in the magnetic trap by RF evaporation. In such a low temperature, the loss of magnetic trap (Majorana loss) will prevent the atoms from reaching a high density, and the atoms cannot be cooled further. To reduce the loss rate of the magnetic trap, the far blue detuning light (532 nm, 18 W) is added to plug the zero point of the magnetic trap. In the optically plugged magnetic trap, atoms with high density are cooled down enough, which gives a good start for the loading of optical dipole trap.

Acta Physica SinicaJan 1, 20174 citations

Evaporative Cooling and Bose-Einstein Condensation of Two Hyperfine States of 87 Rb

J. R. Ensher, D. S. Jin, M. R. Matthews +2 more

In comparing evaporative cooling to Bose-Einstein Condensation in the F=2, mf= 2 and F=l, mf= -1 states of 87Rb we observe fewer condensate F=2 atoms, in contrast with a simple model.

Quantum Electronics and Laser Science ConferenceMay 18, 19970 citations

Production of87Rb Bose—Einstein condensates in a hybrid trap

Yafan Duan, Bo-Nan Jiang, Jian-Fang Sun +3 more

We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum degeneracy: initial radio-frequency (RF) enforced evaporative cooling in the quadrupole magnetic trap and further runaway evaporative cooling in the optical dipole trap. The hybrid trap does not require a very high power laser such as that in the traditional pure optical trap, but still has a deep trap depth and a large trap volume, and has better optical access than the normal magnetic trap like the quadrupole-Ioffe-configuration (QUIC) cloverleaf trap. A high trap frequency can be easily realized in the hybrid trap to enhance the elastic collision rate and shorten the evaporative cooling time. In our experiment, pure Bose—Einstein condensates (BECs) with about 1 × 10 5 atoms can be realized in 6 s evaporative cooling in the optical dipole trap.We report a rapid evaporative cooling method using a hybrid trap which is composed of a quadrupole magnetic trap and a one-beam optical dipole trap. It contains two kinds of evaporative coolings to reach the quantum degeneracy: initial radio-frequency (RF) enforced evaporative cooling in the quadrupole magnetic trap and further runaway evaporative cooling in the optical dipole trap. The hybrid trap does not require a very high power laser such as that in the traditional pure optical trap, but still has a deep trap depth and a large trap volume, and has better optical access than the normal magnetic trap like the quadrupole-Ioffe-configuration (QUIC) cloverleaf trap. A high trap frequency can be easily realized in the hybrid trap to enhance the elastic collision rate and shorten the evaporative cooling time. In our experiment, pure Bose—Einstein condensates (BECs) with about 1 × 10 5 atoms can be realized in 6 s evaporative cooling in the optical dipole trap.

Chinese Physics BMay 1, 20134 citations

Radio-frequency-induced evaporative cooling of

{}^{87}\mathrm{Rb}

atoms in the

F=2,

m=2

ground state in a magnetic trap with a high bias field is found to be hampered, and eventually interrupted, by the presence of nonlinear Zeeman shifts. An experiment studying evaporation at a fixed adjustable rf frequency was used to illustrate this effect. These nonlinear shifts prevent us from reaching quantum degeneracy in the

F=2,

m=2

ground state; however, evaporation in the

F=1,

$m=\ensuremath{-}1$ ground state is not adversely affected, and we can produce a Bose-Einstein condensate (BEC). Our analysis shows that this effect can play a role in many BEC experiments.