Optical Loading of Magnetic Traps

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Revision as of 12:43, 9 February 2014 by Ivan K (Talk | contribs) (Overview)

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Post Docs

  • Hsin-I Lu
  • Boerge Hemmerling

Grad Students

  • Ivan Kozyryev
  • Louis Baum

Undergrad Students

  • Michael Casson

Overview

A buffer gas cooled beam of CaH will be separated from helium buffer gas before being optically loaded into a magnetic trap.

General approaches for delivering cold, chemically diverse molecules in large quantities could have a profound impact on research in quantum simulation, cold controlled chemistry, and particle physics. 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 He buffer gas. In the current experiment, we produce a cold and slow CaF molecular beam with initial 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. Molecules are optical pumped between low and high field seeking states to slow and load them into a 4 Tesla deep magnetic trap. Since the trap loading scheme requires scattering of only a few photons, the method is applicable for many molecules.

We choose to study CaH molecules because of its good collisional properties. The elastic to spin-depolarization collision ratio between CaH and He is measured to be larger than 10^5. Theoretical study shows the main spin-depolarization mechanism of doublet Sigma molecules during collisions with Helium is due to mixing of the molecular wavefunction between rotational ground and excited states. The spin-rotational coupling in the rotational excited state can cause spin-depolarization. Since CaH has large rotational splitting (12K between N=0 and N=1 states), we expect it to maintain its spin orientation during collisions with other S state atoms. In addition, magnetic dipolar relaxation should be comparable to collisions between alkali atoms due to its moderate magnetic dipole moment. These properties make it a good candidate for sympathetic cooling of molecules.

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