Optical Loading of Magnetic Traps

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People

Post Docs

  • Hsin-I Lu
  • Boerge Hemmerling

Grad Students

  • Ivan Kozyryev
  • Louis Baum

Undergrad Students

  • Michael Casson

Overview

A schematic diagram of magnetic trapping using optical loading and magnetic slowing for CaF

General approaches for delivering cold, chemically diverse molecules in large quantities could have a profound impact on research in quantum simulation [1], cold controlled chemistry [2, 3], and particle physics [4, 5]. Buffer gas loading of polar molecules into magnetic traps has been demonstrated with many species including CaH and NH. However, increasing phase space density via evaporative or sympathetic cooling was previously inhibited by collisions with residual helium (He) buffer gas. In the current experiment, we produce a cold and slow calcium monofluoride (CaF) molecular beam with initial forward velocity around 30 m/s and load CaF (v=0, N=1) into a deep superconducting magnetic trap combining magnetic deceleration and optical pumping. A magnetic lens is used to collimate low-field seeking states. Irreversible trap loading is achieved using two optical pumping stages, where scattered photons remove molecular potential energy and entropy. Using a cryogenic shutter to block the buffer gas after trap loading, we observe a trap lifetime exceeding 500 ms, limited by background He collisions. Since the trap loading scheme requires scattering of only a few photons, the method is applicable to a wide range of magnetic species, including polyatomic molecules.

Currently, we are pursuing co-trapping of calcium monohydride (CaH) molecules with lithium (Li) atoms for studying Li-CaH collisions. We have already produced a slow beam of CaH [6] and previous theoretical work [7] predicts good collisional properties for the chosen atom-molecule pair. Moreover, since CaH has a larger rotational constant than CaF, we are able to operate our trap at its maximum capacity.

[1] Micheli et al., Nature Physics 2, 341 (2006). [2] Ospelkaus et al., Science 327, 853 (2010). [3] De Miranda et al., Nature Physics 7, 502 (2011). [4] Hudson et al., Nature 473, 493 (2011). [5] Baron et al., Science 343, 269 (2014). [6] Lu et al., Phys. Chem. Chem. Phys. 13, 42 (2011). [7] Tscherbul et al., Phys. Rev. A 84, 4 (2011).

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