Difference between revisions of "Optical Loading of Magnetic Traps"
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==Overview== | ==Overview== | ||
[[File:Apparatus_for_Magnetically_Trapping_CaH.png|thumb|500px|A buffer gas cooled beam of CaH will be separated from helium buffer gas before being optically loaded into a magnetic trap.]] | [[File:Apparatus_for_Magnetically_Trapping_CaH.png|thumb|500px|A buffer gas cooled beam of CaH will be separated from helium buffer gas before being optically loaded into a magnetic trap.]] | ||
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| + | Buffer gas loading of polar molecules into magnetic traps has been demonstrated with many molecules including CaH and | ||
| + | NH. However, increasing phase space density via evaporative cooling or sympathetic cooling is inhibited by collisions with residual buffer gas. In the current experiment, we plan to produce a cold and clean CaH molecular beam and load CaH into a deep | ||
| + | magnetic trap combining magnetic deceleration and optical pumping. A magnetic guide separates CaH molecules from a buffer gas beam source to produce a cold, clean molecular beam. 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. | ||
==Recent Publications== | ==Recent Publications== | ||
* [[Media:New_journal_of_physics_11_2009.pdf |Intense atomic and molecular beams via neon buffer-gas cooling]], D. Patterson, J. Rasmussen, and J.M. Doyle. New Journal of Physics 11, 055018 (2009). | * [[Media:New_journal_of_physics_11_2009.pdf |Intense atomic and molecular beams via neon buffer-gas cooling]], D. Patterson, J. Rasmussen, and J.M. Doyle. New Journal of Physics 11, 055018 (2009). | ||
*[http://jsbach.harvard.edu/resources/bufferprints/oxygen_beam.pdf Bright, Guided Molecular Beam with Hydrodynamic Enhancement], D. Patterson and J.M. Doyle. J of Chem Phys 126, 154307 (2007). | *[http://jsbach.harvard.edu/resources/bufferprints/oxygen_beam.pdf Bright, Guided Molecular Beam with Hydrodynamic Enhancement], D. Patterson and J.M. Doyle. J of Chem Phys 126, 154307 (2007). | ||
Revision as of 09:22, 9 November 2010
Contents
Cold Beam
People
Post Docs
- Matthew Wright
Grad Students
- Hsin-I Lu
- Julia Rasmussen
Overview
Buffer gas loading of polar molecules into magnetic traps has been demonstrated with many molecules including CaH and NH. However, increasing phase space density via evaporative cooling or sympathetic cooling is inhibited by collisions with residual buffer gas. In the current experiment, we plan to produce a cold and clean CaH molecular beam and load CaH into a deep magnetic trap combining magnetic deceleration and optical pumping. A magnetic guide separates CaH molecules from a buffer gas beam source to produce a cold, clean molecular beam. 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.
Recent Publications
- Intense atomic and molecular beams via neon buffer-gas cooling, D. Patterson, J. Rasmussen, and J.M. Doyle. New Journal of Physics 11, 055018 (2009).
- Bright, Guided Molecular Beam with Hydrodynamic Enhancement, D. Patterson and J.M. Doyle. J of Chem Phys 126, 154307 (2007).
