Neutral 7Li and 6Li atoms are laser cooled and trapped using the 22P3/2(F=3)↔22S1/2(F=2) and 22P3/2(F=5/2)↔22S1/2(F=3/2) transitions, respectively. The Zeeman tuning is employed in the deceleration stage. Using a magneto-optical trap with a tetrahedral laser-beam configuration the atomic density of 3×109 atoms/cm3 is obtained for 7Li and a half of that for 6Li. The measured temperature of the trapped 7Li atoms is 350±40 µK when the detuning is 8 MHz to the red.
Neutral 7Li and 6Li atoms are laser cooled and trapped using the 22P3/2(F=3)↔22S1/2(F=2) and 22P3/2(F=5/2)↔22S1/2(F=3/2) transitions, respectively. The Zeeman tuning is employed in the deceleration stage. Using a magneto-optical trap with a tetrahedral laser-beam configuration the atomic density of 3×109 atoms/cm3 is obtained for 7Li and a half of that for 6Li. The measured temperature of the trapped 7Li atoms is 350±40 µK when the detuning is 8 MHz to the red.
To prepare cold lithium atoms for atomic interferometry experiments, we have carried out experimental researches on Zeeman deceleration and magneto-optical trap (MOT) of lithium atoms. We have also designed and implemented a compact adjustable Zeeman slower with an inner water cooling chamber, to decelerate the velocity of the 7Li atom beam from 600 m/s down to 60 m/s, and load them into the MOT. The loading rate is 5108 /s, the total trapped atom number is 1109 , and the lowest temperature of the atom cloud is 220 30 K. Then we investigate the dependence of lifetime of 7Li atoms in optical molasses on the detuning of trapping laser beams. The above results lay a foundation for further sub-Doppler cooling, optical trap based on evaporative cooling, and atomic interferometry experiments.
A setup for laser cooling and confining of 7 Li atoms in a magneto-optical trap has been built. The possibility of cooling and trapping of 7 Li atoms in a wide range of frequency detuning of the cooling laser has been proved experimentally. Independent information on the density and number of ultracold 7 Li atoms on various ground-state sublevels, as well as on the temperature of the atoms, has been obtained with the use of a probing tunable laser. This information is important for preparing an ultracold plasma and Rydberg matter.
Lithium is an important element in atomic quantum gas experiments because its interactions are highly tunable due to broad Feshbach resonances and zero-crossings and because it has two stable isotopes: 6Li, a fermion, and 7Li, a boson. Although lithium has special value for these reasons, it also presents experimental challenges. In this article, we review some of the methods that have been developed or adapted to confront these challenges, including beam and vapor sources, Zeeman slowers, sub-Doppler laser cooling, laser sources at 671 nm, and all-optical methods for trapping and cooling. Additionally, we provide spectral diagrams of both 6Li and 7Li and present plots of Feshbach resonances for both isotopes.
The advent of the laser opened the way to the development of powerful new methods for manipulating and cooling atoms which were exploited in the realization of Bose–Einstein condensation in alkali atom vapours. To set the stage we describe a typical experiment, which is shown schematically in Fig. 4.1. A beam of sodium atoms emerges from an oven at a temperature of about 600 K, corresponding to a speed of about 800 m s –1 , and is then passed through a so-called Zeeman slower, in which the velocity of the atoms is reduced to about 30 m s –1 , corresponding to a temperature of about 1 K. In the Zeeman slower, a laser beam propagates in the direction opposite that of the atomic beam, and the radiation force produced by absorption of photons retards the atoms. Due to the Doppler effect, the frequency of the atomic transition in the laboratory frame is not generally constant, since the atomic velocity varies. However, by applying an inhomogeneous magnetic field designed so that the Doppler and Zeeman effects cancel, the frequency of the transition in the rest frame of the atom may be held fixed. On emerging from the Zeeman slower the atoms are slow enough to be captured by a magneto-optical trap (MOT), where they are further cooled by interactions with laser light to temperatures of order 100 μK. Another way of compensating for the changing Doppler shift is to increase the laser frequency in time, which is referred to as ‘chirping’. In other experiments the MOT is filled by transferring atoms from a second MOT where atoms are captured directly from the vapour.
A two element magneto-optical trap (MOT) in standard configuration for Na and 7Li or 6Li is used to cool and trap Na and one Li isotope simultaneously or separately. The metal background vapor out of which the atoms are trapped comes from dispensers. The two atom clouds can be slightly shifted what makes it easy to overlap them. The number and density of the clouds were determined and the temperature measured roughly. The mutual influence of the clouds was investigated and turned out to be smaller than the noise. Preliminary experiments working towards the production of heteronuclear cold molecules by photoassociation were performed, showing the well known production of Na2 long- range molecules. Additionally, the photoionization cross- section was determined by ionizing cold atoms in the excited state by UV-laser light. The results are in reasonable agreement with data obtained elsewhere using synchrotron radiation.
The advent of the laser opened the way to the development of powerful methods for producing and manipulating cold atomic gases. To set the stage we describe a typical experiment, which is shown schematically in Fig. 4.1. A beam of sodium atoms emerges from an oven at a temperature of about 600 K, corresponding to a speed of about 800 m s −1 , and is then passed through a so-called Zeeman slower, in which the velocity of the atoms is reduced to about 30 m s −1 , corresponding to a temperature of about 1 K. In the Zeeman slower, a laser beam propagates in the direction opposite that of the atomic beam, and the radiation force produced by absorption of photons retards the atoms. Due to the Doppler effect, the frequency of the atomic transition in the laboratory frame is not generally constant, since the atomic velocity varies. However, by applying an inhomogeneous magnetic field designed so that the Doppler and Zeeman effects cancel, the frequency of the transition in the rest frame of the atom may be held fixed. On emerging from the Zeeman slower the atoms are slow enough to be captured by a magneto-optical trap (MOT), where they are further cooled by interactions with laser light to temperatures of order 100 μK. Another way of compensating for the changing Doppler shift is to increase the laser frequency in time, which is referred to as ‘chirping’.