SYMPATHETICAL LASER COOLING OF MOLECULAR IONS TO THE $\mu$K REGIME
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Date
2008
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Ohio State University
Abstract
The complexity of molecular spectra prevents direct laser cooling of most molecules. Molecular ions can be indirectly laser-cooled by a Columbic interaction with a neighboring atomic ion. This sympathetic cooling method has been used to lower the temperature of molecular ions ranging from CaO$^{+}$ to C$_{60}^{+}$ to less than 100 mK by Doppler cooling the atomic ions}rensen \textit{Phys.~Rev.~Lett.} \underline{\textbf{93}}, 243201 (2004). V.~L.~Ryjkov, XZ.~Zhao and H.~A.~Schuessler \textit{Phys.~Rev.~A} \underline{\textbf{74}}, 023401 (2006). A.~Ostendorf, C.~B.~Zhang, M.~A.~Wilson, D.~Offenberg, B.~Roth, and S.~Schiller \textit{Phys.~Rev.~Lett.} \underline{\textbf{97}}, 243005 (2006).}. Starting with two ions of Ca$^{+}$ in the trap, we introduce oxygen gas until one CaO$^{+}$ is produced. The motion of a CaO$^{+}$ molecular ion and a Ca$^{+}$ atomic ion are coupled by the Coulomb interaction in the same trap. The frequencies of the normal modes of the atom-molecule crystal are first measured by observing the fluorescence quenching of the Ca$^{+}$ atoms. The normal modes can be cooled to the motional ground state by addressing the sidebands of the Ca$^{+}$ quadrupole transition. The result is an atom-molecule crystal with a translational temperature in the $\mu$K regime.
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M. Drewsen, A. Mortensen, R. Martinussen, P. Staanum and J. L. S\o
Author Institution: School of Chemistry and Biochemistry and Computational Science and Engineering; Division, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
Author Institution: School of Chemistry and Biochemistry and Computational Science and Engineering; Division, Georgia Institute of Technology, Atlanta, Georgia 30332, USA