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

Abstract

Magnetically trapped neutral atoms can be cooled with the evaporation technique. This is typically done by using a radiofrequency (rf) field that adiabatically couples trapped and untrapped internal atomic states for atoms with kinetic energies above a value set by the field frequency. The rf-field can also induce nonadiabatic changes of internal atomic spin states (F,M) that lead to heating and enhanced loss of atoms. In this paper we use wave packet simulations to show that the evaporation process can induce these nonadiabatic transitions which change the internal spin state of doubly spin-polarized (2,2) trapped atoms. We also verify the validity of a multistate Landau-Zener model in describing the nonadiabatic dynamics. In addition, we calculate exchange relaxation rate coefficients for collisions between atoms in the (2,M) states of 23-Na atoms. Large exchange relaxation coefficients for 23-Na as compared to 87-Rb F=2 suggest that evaporative cooling of (2,2) Na will be more difficult than for the corresponding state of Rb.

13 pages, RevTex, 5 embedded eps figures

References in corpus (3)

• Dynamical response of a Bose-Einstein condensate to a discontinuous change in internal state
• Time-dependent control of ultracold atoms and Bose-Einstein condensates in magnetic traps
• Wave packet dynamics with Bose-Einstein condensates

Cited by in corpus (9)

• Radio-frequency dressed state potentials for neutral atoms
• Fast noise in the Landau-Zener theory
• Fifteen classes of solutions of the quantum two-state problem in terms of the confluent Heun function
• Superparabolic Level Glancing Models for Two-State Quantum Systems
• Theory of strong outcoupling from Bose-Einstein condensates
• Enhancement of On-Site Interactions of Tunnelling Ultracold Atoms in Optical Potentials using Radio-Frequency Dressing
• Collective excitations in a F=2 Bose-Einstein condensate
• Four-Wave Mixing In BEC Systems With Multiple Spin States
• Atomic dynamics in evaporative cooling of trapped alkali atoms in strong magnetic fields