Difference between revisions of "Optical Loading of Magnetic Traps"

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==People==
 
==People==
−
===Post Docs===
 
−
*Matthew Wright
 
 
===Grad Students===
 
===Grad Students===
 +
*Ivan Kozyryev
 +
*Louis Baum
 +
 +
===Undergrad Students===
 +
*Alex Sedlack
 +
 +
===Former Students and Post Docs===
 +
*Boerge Hemmerling
 
*Hsin-I Lu
 
*Hsin-I Lu
−
*Julia Rasmussen
+
*Julia Piskorski
 +
*Michael Casson
 +
*Peter Olson
 +
*Kyle Matsuda
  
 
==Overview==
 
==Overview==
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[[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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<html><iframe width="480" height="293" src="//www.youtube.com/embed/xAsiwVdpU1w" frameborder="0" allowfullscreen></iframe></html>
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 +
 
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[[File:OPL_apparatus.gif|thumb|500px|A schematic diagram of magnetic trapping using optical loading and magnetic slowing for CaF]]
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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 focus 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.
  
−
Buffer gas loading of polar molecules into magnetic traps has been demonstrated with many molecules including CaH and
+
In parallel, we are also working toward the optical loading and magnetic trapping of small polyatomic molecules. We have already buffer-gas cooled SrOH and studied its inelastic collisions with He. The electronic structure of this triatomic molecule is similar to that of CaF and SrF. Moreover, optical pumping and detection of SrOH in our experiment can be performed with all solid-state diode lasers. We are planning on co-trapping of SrOH and K for studying atom-molecule collisions and exploring the possibility of sympathetic cooling for polyatomic molecules.  
−
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
+
* [1] Micheli et al., Nature Physics 2, 341 (2006).
−
between CaH and He is measured to be larger than 10^5. Theoretical study shows the main
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* [2] Ospelkaus et al., Science 327, 853 (2010).
−
spin-depolarization mechanism of doublet Sigma molecules during collisions with Helium is due to mixing
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* [3] De Miranda et al., Nature Physics 7, 502 (2011).
−
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
+
* [4] Hudson et al., Nature 473, 493 (2011).
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has large rotational splitting (12K between N=0 and N=1 states), we expect it to maintain
+
* [5] Baron et al., Science 343, 269 (2014).
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its spin orientation during collisions with other S state atoms. In addition, magnetic dipolar
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* [6] Lu et al., Phys. Chem. Chem. Phys. 13, 42 (2011).
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relaxation should be comparable to collisions between alkali atoms due to its moderate
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* [7] Tscherbul et al., Phys. Rev. A 84, 4 (2011).
−
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).
+
* [1] I. Kozyryev, L. Baum, K. Matsuda, P. Olson, B. Hemmerling, and J. M. Doyle,  '''Collisional relaxation of vibrational states of SrOH with He at 2 K''', [http://dx.doi.org/10.1088/1367-2630/17/4/045003 New Journal of Physics 17, 045003 (2015)].
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*[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).
+
* [2] H.-I Lu, I. Kozyryev, B. Hemmerling, J. Piskorski, and J. M. Doyle, '''Magnetic Trapping of Molecules via Optical Loading and Magnetic Slowing''', [http://dx.doi.org/10.1103/PhysRevLett.112.113006 Phys. Rev. Lett. 112, 113006 (2014)].
 +
* [3] Hsin-I Lu, Julia Rasmussen, Matthew J. Wright, Dave Patterson, and John M. Doyle, '''Cold and Slow Molecular Beam''', [http://dx.doi.org/10.1039/c1cp21206k Phys. Chem. Chem. Phys. (2011)].
 +
* [4] D. Patterson, J. Rasmussen, and J.M. Doyle, '''Intense atomic and molecular beams via neon buffer-gas cooling''', [http://dx.doi.org/10.1088/1367-2630/11/5/055018 New Journal of Physics 11, 055018 (2009)].
 +
* [5] D. Patterson and J.M. Doyle, '''Bright, Guided Molecular Beam with Hydrodynamic Enhancement''', [http://dx.doi.org/10.1063/1.2717178 J. of Chem Phys 126, 154307 (2007)]

Latest revision as of 14:54, 28 October 2016

People

Grad Students

  • Ivan Kozyryev
  • Louis Baum

Undergrad Students

  • Alex Sedlack

Former Students and Post Docs

  • Boerge Hemmerling
  • Hsin-I Lu
  • Julia Piskorski
  • Michael Casson
  • Peter Olson
  • Kyle Matsuda

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 focus 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.

In parallel, we are also working toward the optical loading and magnetic trapping of small polyatomic molecules. We have already buffer-gas cooled SrOH and studied its inelastic collisions with He. The electronic structure of this triatomic molecule is similar to that of CaF and SrF. Moreover, optical pumping and detection of SrOH in our experiment can be performed with all solid-state diode lasers. We are planning on co-trapping of SrOH and K for studying atom-molecule collisions and exploring the possibility of sympathetic cooling for polyatomic molecules.

  • [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).

Recent Publications

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