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Title: Ultracold Molecule Production via a Resonant Oscillating Magnetic Field

Abstract

A novel atom-molecule conversion technique has been investigated. Ultracold {sup 85}Rb atoms sitting in a dc magnetic field near the 155 G Feshbach resonance are associated by applying a small sinusoidal oscillation to the magnetic field. There is resonant atom to molecule conversion when the modulation frequency closely matches the molecular binding energy. We observe that the atom to molecule conversion efficiency depends strongly on the frequency, amplitude, and duration of the applied modulation and on the phase space density of the sample. This technique offers high conversion efficiencies without the necessity of crossing or closely approaching the Feshbach resonance and allows precise spectroscopic measurements. Efficiencies of 55% have been observed for pure Bose-Einstein condensates.

Authors:
; ;  [1];  [2]
  1. JILA, National Institute of Standards and Technology (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20699523
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 95; Journal Issue: 19; Other Information: DOI: 10.1103/PhysRevLett.95.190404; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ATOM-ATOM COLLISIONS; ATOMS; BINDING ENERGY; BOSE-EINSTEIN CONDENSATION; MAGNETIC FIELDS; MODULATION; MOLECULES; OSCILLATIONS; PHASE SPACE; RESONANCE; RUBIDIUM 85

Citation Formats

Thompson, S.T., Hodby, E., Wieman, C.E., and University of Colorado, and the Department of Physics, University of Colorado, Boulder, Colorado 80309-0440. Ultracold Molecule Production via a Resonant Oscillating Magnetic Field. United States: N. p., 2005. Web. doi:10.1103/PhysRevLett.95.190404.
Thompson, S.T., Hodby, E., Wieman, C.E., & University of Colorado, and the Department of Physics, University of Colorado, Boulder, Colorado 80309-0440. Ultracold Molecule Production via a Resonant Oscillating Magnetic Field. United States. doi:10.1103/PhysRevLett.95.190404.
Thompson, S.T., Hodby, E., Wieman, C.E., and University of Colorado, and the Department of Physics, University of Colorado, Boulder, Colorado 80309-0440. Fri . "Ultracold Molecule Production via a Resonant Oscillating Magnetic Field". United States. doi:10.1103/PhysRevLett.95.190404.
@article{osti_20699523,
title = {Ultracold Molecule Production via a Resonant Oscillating Magnetic Field},
author = {Thompson, S.T. and Hodby, E. and Wieman, C.E. and University of Colorado, and the Department of Physics, University of Colorado, Boulder, Colorado 80309-0440},
abstractNote = {A novel atom-molecule conversion technique has been investigated. Ultracold {sup 85}Rb atoms sitting in a dc magnetic field near the 155 G Feshbach resonance are associated by applying a small sinusoidal oscillation to the magnetic field. There is resonant atom to molecule conversion when the modulation frequency closely matches the molecular binding energy. We observe that the atom to molecule conversion efficiency depends strongly on the frequency, amplitude, and duration of the applied modulation and on the phase space density of the sample. This technique offers high conversion efficiencies without the necessity of crossing or closely approaching the Feshbach resonance and allows precise spectroscopic measurements. Efficiencies of 55% have been observed for pure Bose-Einstein condensates.},
doi = {10.1103/PhysRevLett.95.190404},
journal = {Physical Review Letters},
number = 19,
volume = 95,
place = {United States},
year = {Fri Nov 04 00:00:00 EST 2005},
month = {Fri Nov 04 00:00:00 EST 2005}
}
  • We study the process of the production of ultracold molecules from ultracold atoms using a sinusoidally oscillating magnetic-field modulation. Our study is based on a two-mode mean-field treatment of the problem. When the magnetic field is resonant roughly with the molecular binding energy, Shapiro-like resonances are observed. Their resonance profiles are well fitted by the Lorentzian functions. The linewidths depend on both the amplitude and the duration of the applied modulations and are found to be dramatically broadened by the thermal dephasing effect. The resonance centers shift due to both the many-body effect and the finite temperature effect. Our theorymore » is consistent with a recent experiment [S. T. Thompson, E. Hodby, and C. E. Wieman, Phys. Rev. Lett. 95, 190404 (2005)]. Our model predicts a 1/3 ceiling for the molecular production yield in uncondensed ultracold atomic clouds for a long coupling time, while for condensed atoms the optimal conversion yield could be beyond the limit.« less
  • The effect of random magnetic fields on the dissociation of ultracold molecules with Feshbach resonances is studied analytically. The dissociation spectrum and the evolution of the molecule fraction are obtained for a general form of the magnetic-field ramp and different noise properties relevant to standard experimental conditions. The results uncover the robustness against noise of some characteristics of the dissociation process, in particular, of the dependence of the mean atomic kinetic energy on the system parameters. Implications for the applicability of a method proposed to determine the width of the Feshbach resonances from the measurement of the dissociation spectrum aremore » analyzed. Moreover, we discuss how the presence of fluctuations can affect the use of particular ramp shapes to tailor the properties of the generated atomic distribution.« less
  • A simple equation is derived describing the generation of the quasi-steady magnetic field by resonant absorption in a cold, collisionless plasma. An initial value problem is solved to ascertain the explicit time behavior of the high frequency fields due to resonant absorption. These fields are employed to obtain a fully analytic expression for the quasi-steady magnetic field. Expressions are also presented for the saturated magnetic field based on saturation times for the high frequency fields appropriate to plasma wave convection or wavebreaking. Modifications of the magnetic field structure due to plasma wave propagation are also calculated and the magnetic fieldmore » is seen to convect with the plasma wave.« less
  • We have observed the formation of ground-state Na{sub 2} molecules via the spontaneous decay of excited molecules created by the photoassociation of ultracold atoms. We measure the binding energies of molecules created in three hyperfine components of the lowest singlet and triplet potentials of Na{sub 2} by two different methods. Two of the features are purely triplet a {sup 3}{sigma}{sub u}{sup +} (v=15) (quasibound) states that have not been previously observed, while the third is a mixed X {sup 1}{sigma}{sub g}{sup +}-a {sup 3}{sigma}{sub u}{sup +} state. The molecules are detected with high-resolution cw laser ionization techniques and binding energiesmore » are measured to within 10 MHz.« less