A magneto-optical trap for chromium with population repumping via intercombination lines

Bell, A. S.; Stühler, J.; Locher, S.; Hensler, S.; Mlynek, J.; Pfau, Tilman

doi:10.1209/epl/i1999-00140-7

Cited by 45 publications

(36 citation statements)

References 14 publications

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“…The magnetic dipoledipole interaction is much stronger than for alkalis and may lead to to a BCS-like transition in a degenerate Fermi gas of 53 Cr [17]. In addition, chromium has technological potential in nanostructure fabrication [18,19] and structured doping [20] [14]. To our knowledge, the lifetime τ D of these metastable states has not been measured to date but a lower limit of τ D > 50 s can be deduced from our MT decay times.…”

Section: Fig 1 Relevant Part Of Thementioning

confidence: 83%

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Continuous loading of a magnetic trap

et al. 2001

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We have realized a scheme for continuous loading of a magnetic trap (MT).52 Cr atoms are continuously captured and cooled in a magneto-optical trap (MOT). Optical pumping to a metastable state decouples atoms from the cooling light. Due to their high magnetic moment (6 µB), low-field seeking metastable atoms are trapped in the magnetic quadrupole field provided by the MOT. Limited by inelastic collisions between atoms in the MOT and in the MT, we load 10 8 metastable atoms at a rate of 10 8 atoms/s below 100 µK into the MT. Optical repumping after the loading allows us to realize a MT of ground state chromium atoms. Although multiply loading of a MT has been achieved [10] experiments so far suffer from the absence of a method for efficient cw loading of atoms into a BEC. Hence to date a matter wave analogon to the continuous wave optical laser has not been realized. Alternatively, a cw atom laser based on magnetic guiding in combination with atomic collisions was suggested [11]. In addition, cw loading of low-dimensional optical traps with laser cooled atoms was proposed [12] and recently demonstrated [13].In this letter we report on the cw loading of a three dimensional conservative trap with laser cooled atoms that are decoupled from all light fields present. We show that atoms can be optically pumped within a chromium magneto-optical trap (MOT) [14,15] into metastable "dark" states and stored in a MT built up by the quadrupole magnetic field of the MOT. We present results of systematic studies on the loading process and on the lifetime of the MT. Using the cw loading mechanism and a final repumping process we obtain good starting conditions for experiments towards degenerate quantum gases with ground state chromium atoms.Our cw loading scheme consists of an atomic reservoir and a conservative trap overlapped in space and time. The reservoir is prepared by cooling atoms in a MOT on a transition |g → |e (FIG. 1). A weak decay channel |e → |d allows the transfer of reservoir atoms into an additional long lived and trapped state |d in which atoms can be accumulated. In our realization low field seeking Zeeman substates of |d are trapped in the magnetic quadrupole field of the MOT. The loading can be very efficient if |d atoms are decoupled from the MOT light and if their kinetic energy is smaller than the conservative trap depth. A large decay rate branching ratio (Γ eg /Γ ed ≫ 1) assures a steady state MOT in thermal equilibrium and is expected to greatly reduce reabsorption of transfer photons by atoms in the MT [16]. MT FIG. 1. Relevant part of the52 Cr level scheme. The MOT involves all levels and transitions, the continuous loading process of the magnetic trap (MT) relies on the Λ-system depicted in black (levels |g , |e , |d ).Chromium combines the desired Λ-like level scheme (FIG. 1, black levels and transitions) with a high magnetic moment of up to 6 µ B (µ B =Bohr's magneton). Due to its isotopic composition (3 bosons:52 Cr (84%), 50 Cr (4%), 54 Cr (2%), and one fermion: 53 Cr (10%) ) it is a promising e...

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Section: Fig 1 Relevant Part Of Thementioning

confidence: 83%

“…We show that atoms can be optically pumped within a chromium magneto-optical trap (MOT) [14,15] into metastable "dark" states and stored in a MT built up by the quadrupole magnetic field of the MOT. We present results of systematic studies on the loading process and on the lifetime of the MT.…”

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Continuous loading of a magnetic trap

et al. 2001

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“…For example, the dipole moment of the fermionic deuterated ammonia molecule 15 ND 3 is d = 1.5 D, which corresponds to an effective scattering length (see above, Eq. (6) Another possibility is to use magnetic atomic dipoles [33][34][35][36][37][38]. Chromium atoms have a magnetic moment µ = 6µ B , which is equivalent to an electric dipole moment of d * = 6·10 −2 D, and an effective scattering length a d = −5Å.…”

Section: Physical Realizations Of Ultracold Dipolar Gasesmentioning

confidence: 99%

Ultracold Dipolar Gases – a Challenge for Experiments and Theory

Baranov

Dobrek

Góral

et al. 2003

Condensation and Coherence in Condensed Matter

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We present a review of recent results concerning the physics of ultracold trapped dipolar gases. In particular, we discuss the Bose-Einstein condensation for dipolar Bose gases and the BCS transition for dipolar Fermi gases. In both cases we stress the dominant role of the trap geometry in determining the properties of the system. We present also results concerning bosonic dipolar gases in optical lattices and the possibility of obtaining variety of different quantum phases in such case. Finally, we analyze various possible routes towards achieving ultracold dipolar gases.

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“…Atoms are magnetically trapped in a long-lived metastable state which is decoupled from the MOT light. Transfer between MOT and MT is provided by radiative leakage [12,5,6] from the excited state, which is populated by the MOT laser. We have implemented this scheme with atomic chromium, but also the alkaline earth metals and e.g.…”

Section: Introductionmentioning

confidence: 99%

Continuous loading of cold atoms into a Ioffe Pritchard magnetic trap

Schmidt¹,

Hensler²,

Werner³

et al. 2003

J. Opt. B: Quantum Semiclass. Opt.

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Abstract. We present a robust continuous optical loading scheme for a IoffePritchard (IP) type magnetic trap. Atoms are cooled and trapped in a modified magneto-optical trap (MOT) consisting of a conventional 2D-MOT in radial direction and an axial molasses. The radial magnetic field gradient needed for the operation of the 2D-MOT is provided by the IP trap. A small axial curvature and offset field provide magnetic confinement and suppress spin-flip losses in the center of the magnetic trap without altering the performance of the 2D-MOT. Continuous loading of atoms into the IP trap is provided by radiative leakage from the MOT to a metastable level which is magnetically trapped and decoupled from the MOT light. We are able to accumulate 30 times more atoms in the magnetic trap than in the MOT. The absolute number of 2×10 8 atoms is limited by inelastic collisions. A model based on rate equations shows good agreement with our data. Our scheme can also be applied to other atoms with similar level structure like alkaline earth metals.

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A magneto-optical trap for chromium with population repumping via intercombination lines

Cited by 45 publications

References 14 publications

Continuous loading of a magnetic trap

Continuous loading of a magnetic trap

Ultracold Dipolar Gases – a Challenge for Experiments and Theory

Continuous loading of cold atoms into a Ioffe Pritchard magnetic trap

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