Microwave state transfer and adiabatic dynamics of magnetically trapped polar molecules

Benjamin K. Stuhl, Mark Yeo, Brian C. Sawyer, Matthew T. Hummon, and Jun Ye

Phys. Rev. A 85, 033427 – Published 30 March 2012

Abstract

Cold and ultracold polar molecules with nonzero electronic angular momenta are of great interest for studies in quantum chemistry and control, investigations of novel quantum systems, and precision measurement. However, in mixed electric and magnetic fields, these molecules are generically subject to a large set of avoided crossings among their Zeeman sublevels; in magnetic traps, these crossings lead to distorted potentials and trap loss from electric bias fields. We have characterized these crossings in OH by microwave-transferring trapped OH molecules from the upper $| f; M = + \frac{3}{2} 〉$ parity state to the lower $| e; + \frac{3}{2} 〉$ state and observing their trap dynamics under an applied electric bias field. Our observations are very well fit by a simple Landau-Zener model, yielding insight to the rich spectra and dynamics of polar radicals in mixed external fields.

Received 23 August 2011

DOI:https://doi.org/10.1103/PhysRevA.85.033427

Authors & Affiliations

Benjamin K. Stuhl^*, Mark Yeo, Brian C. Sawyer^†, Matthew T. Hummon, and Jun Ye

JILA, National Institute of Standards and Technology and the University of Colorado Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA

^*[email protected]
^†Present address: Ion Storage Group, National Institute of Standards and Technology, Boulder, CO 80305, USA.

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Vol. 85, Iss. 3 — March 2012

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Images

Figure 1
Zeeman structure of OH with bias electric fields: (a) 0 V/cm, (b) 500 V/cm at a $90^{\circ}$ magnetic-to-electric field angle $θ_{E B}$ , (c) 5000 V/cm at $65^{\circ}$ , and (d) 5000 V/cm at $90^{\circ}$ . The crossings $X_{M}$ of the $| e; + \frac{3}{2} 〉$ state with the three $| f; M = {- \frac{3}{2}, - \frac{1}{2}, + \frac{1}{2}} 〉$ states are labeled in (a).Reuse & Permissions
Figure 2
(a) Magnetic field distribution in the permanent magnet quadrupole trap. (b) Electric field distribution created by applying a potential difference to the trap magnets. (c) Spatial location of the avoided crossings $X_{M}$ . (d) Relative angle $θ_{E B}$ between electric and magnetic fields in the trap. White denotes $0^{\circ}$ while black denotes $180^{\circ}$ , implying that the avoided crossings are widest in the gray regions.Reuse & Permissions
Figure 3
Post-ARP $e$ -state population vs applied bias field, with 10 (green triangles), 20 (blue squares), and 40 (red diamond) MHz ARP chirp widths. Solid lines are Monte Carlo simulations of the population transfer using realistic bias and RF field distributions from finite-element calculations, a semiclassical treatment of the Stark detunings, and a homogeneous stray field as a free parameter. Inset: Time-of-flight of the $e$ -state population immediately after ARP, with no applied bias field. The rapid loss through the $X_{+ 1 / 2}$ crossing is clearly visible: the solid line is a fit to a single-exponential loss at a rate of $τ_{dyn}^{- 1}$ .Reuse & Permissions
Figure 4
(a) Loss rate of $| e; M = + \frac{3}{2} 〉$ molecules vs applied electric field. The solid red line is a fit to a simple Landau-Zener model; the green shaded stripe denotes the range of observed loss rates for $| f; + \frac{3}{2} 〉$ molecules. The bias field is turned on 5 ms after the ARP pulse is completed, and thus well after the prompt loss seen in the inset of Fig. 3 is completed. Inset: Widths $δ_{M}$ of the avoided crossings between $| e; + \frac{3}{2} 〉$ and $| f; M 〉$ vs applied electric field, at their respectively maximizing values of $θ_{E B}$ . $δ_{+ 1 / 2}$ is linear with field, while $δ_{- 1 / 2}$ and $δ_{- 3 / 2}$ are cubic. (b) Time-of-flight trace of trap oscillations, observed by loading the trap with a nonzero center-of-mass velocity. The solid red fit yields a trap frequency $ν_{trap} = 1350$ Hz.Reuse & Permissions
Figure 5
Schematic of the microwave system used to transfer OH between $Λ$ -doublet levels.Reuse & Permissions
Figure 6
ARP spectra at several different bias $E$ fields. Points are data while solid lines are simulation results. The Stark-Zeeman broadening due to the avoided crossings is clearly visible.Reuse & Permissions

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