Nonadiabatic dynamics in evaporative cooling of trapped atoms by a radio-frequency field

Suominen, Kalle-Antti; Tiesinga, Eite; Julienne, Paul S.

doi:10.1103/physreva.58.3983

Cited by 18 publications

(25 citation statements)

References 39 publications

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“…Nevertheless we observe no additional loss for atoms trapped in RF potentials compared to the static trap for densities up to 10 15 atoms/cm 3 . We attribute this collisional stability of atoms in the RF dressed states to an argument given in [23,24] for weakly dressed atoms during RF-evaporation in magnetic traps: The RF-fields introduce a variation of the potential on length scales smaller than the original static trap, but still large compared to the scattering length of the atoms. Two colliding atom reside in the same adiabatic state, consequently they can be regarded to be in the same spin state when they approach each other closely.…”

Section: Collisional Stabilitymentioning

confidence: 99%

Radiofrequency-dressed-state potentials for neutral atoms

et al. 2006

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Potentials for atoms can be created by external fields acting on properties like magnetic moment, charge, polarizability, or by oscillating fields which couple internal states. The most prominent realization of the latter is the optical dipole potential formed by coupling ground and electronically excited states of an atom with light. Here we present an experimental investigation of the remarkable properties of potentials derived from radio-frequency (RF) coupling between electronic ground states. The coupling is magnetic and the vector character allows to design state dependent potential landscapes. On atom chips this enables robust coherent atom manipulation on much smaller spatial scales than possible with static fields alone. We find no additional heating or collisional loss up to densities approaching 10 15 atoms / cm 3 compared to static magnetic traps. We demonstrate the creation of Bose-Einstein condensates in RF potentials and investigate the difference in the interference between two independently created and two coherently split condensates in identical traps. All together this makes RF dressing a powerful new tool for micro manipulation of atomic and molecular systems. Dressing of internal states of an atom with an external field is a well known technique in quantum optics [1]. The coupling of atomic states to an oscillating field leads to new eigenstates and eigenenergies in the combined system. These dressed states can form adiabatic potentials, which can be employed for atom trapping and manipulation. The most prominent example is the optical dipole potential [2] created when intense coherent light couples ground and electronically excited states of an atom. To create conservative potentials for coherent manipulation spontaneous relaxation of the excited state has to be avoided and hence the light field has to be far detuned. Consequently the magnitude and shape of the dipole potential is given by the local intensity of the light field. Such far detuned dipole potentials are widely used in ultra cold atom experiments [3].Dressing can also be achieved by coupling hyperfine components of the electronic ground state by a magnetic radio-frequency (RF) or micro-wave (MW) field. Dressed state potentials resulting from RF coupling of two spin states in a magnetic field have been studied in neutron optics [4]. Adiabatic potentials induced by coupling hyperfine states with a micro wave have been proposed in Ref. [5], and a detuned micro-wave has been used for trapping ultra cold Cs atoms [6]. The trapping of neutral atoms with RF induced potentials was proposed in [7] and first demonstrated for thermal Rb atoms [8]. Recently RF dressed state potentials were employed for coherent splitting of a one-dimensional Bose-Einstein condensate and matter-wave interference [9]. In this paper, we give for the first time a full experimental demonstra- * Electronic address: hofferberth@atomchip.org tion and analysis of the remarkable properties of these adiabatic RF dressed state potentials, which make them a versatile ...

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Section: Collisional Stabilitymentioning

confidence: 99%

Radiofrequency-dressed-state potentials for neutral atoms

et al. 2006

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“…1(b)]. The dynamics of atoms as they move past the resonance point can be described with a simple semiclassical model [8], which has been shown to agree very well with fully quantum wave packet calculations [3]. The model, however, can be applied only if the resonances between adjacent M F states occur at the exactly same distance from the trap center.…”

Section: Introductionmentioning

confidence: 89%

“…1 (a). For slowly moving atoms the trapping potential depends on the strength of the magnetic field B but not on its direction [3]. In practice the field is dominated by a constant bias field B bias , which eliminates the Majorana spin flips at the center of the trap.…”

Section: Introductionmentioning

confidence: 99%

Atomic dynamics in evaporative cooling of trapped alkali-metal atoms in strong magnetic fields

Pakarinen

Suominen

2000

Phys. Rev. A

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We investigate how the nonlinearity of the Zeeman shift for strong magnetic fields affects the dynamics of rf field induced evaporative cooling in magnetic traps. We demonstrate for the 87 Rb and 23 Na F = 2 trapping states with wave packet simulations how the cooling stops when the rf field frequency goes below a certain limit (for the 85 Rb F = 2 trapping state the problem does not appear). We examine the applicability of semiclassical models for the strong field case as an extension of our previous work [Phys. Rev. A 58, 3983 (1998)

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“…This probability has a maximum value of about 10% for a transition probability P of 5 3 , and is associated to a precise value of the atomic velocity. When considering all possible velocities, the probability of leaving the trap on m F = -1 averages to less than 10%, much less than for the standard situation where the adiabatic passage has 100% efficiency for almost all velocities 17,19 . The experimental observation on Fig.…”

Section: Interrupted Evaporative Cooling In a High Magnetic Fieldmentioning

confidence: 99%