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All-optical preparation of molecular ions in the rovibrational ground state

Nature Physics volume 6, pages 275–278 (2010)Cite this article

Abstract

In the field of cold quantum matter, control of the motional degrees of freedom of both neutral and charged gas-phase molecules has been achieved for a wide range of species1,2,3,4,5,6,7,8,9,10,11. However, cooling of the internal degrees of freedom remains challenging. Recently, transfer to the internal ground state by sophisticated optical techniques has been demonstrated for neutral alkali dimers created in single quantum states from ultracold atoms12,13,14,15. Here we demonstrate cooling of the rotational degree of freedom of heteronuclear diatomic molecules with a thermal distribution of internal states, using a simple, robust and general optical-pumping scheme with two low-power continuous-wave lasers. With trapped and translationally cooled hydrogen deuteride (HD+) molecular ions as a model system, we achieve 78(4)% rovibrational ground-state population. The rotationally, vibrationally and translationally cold molecular ion ensemble is suitable for a number of applications, such as generation of long-lived coherences or frequency metrology of fundamental constants16,17.

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Figure 1: Schematic view of relevant rovibrational states and dipole transitions in the 1s σ electronic ground state of HD+ (not to scale).
Figure 2: Rate equation simulation for the optical pumping scheme.
Figure 3: Experimental sequence for determining the population pN in the state (v=0,N).
Figure 4: Rotational-state distribution of the vibrational ground state after applying the optical pumping scheme.

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Acknowledgements

The authors thank M. Hansen, S. Vasilyev, E. Zlobina for contributions to the experimental set-up and A. Nevsky for helpful discussions. This work is supported by the Deutsche Forschungsgemeinschaft under grant SCHI 431/11-1.

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Authors and Affiliations

  1. Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany

    T. Schneider, B. Roth, H. Duncker, I. Ernsting & S. Schiller

Authors
  1. T. Schneider
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  2. B. Roth
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  3. H. Duncker
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  4. I. Ernsting
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  5. S. Schiller
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Contributions

T.S. and B.R. planned and carried out the experiments, S.S. and H.D. participated, T.S. carried out data evaluation and numerical simulations, B.R. participated, S.S. and H.D. developed the quantum cascade laser and distributed feedback diode laser system, S.S. conceived the study, developed the rate equation model and analytic treatment, I.E. developed a near-infrared diode laser system and participated in preliminary and complementary investigations; T.S. wrote the paper, B.R. and S.S. participated.

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Correspondence to T. Schneider or S. Schiller.

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The authors declare no competing financial interests.

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Schneider, T., Roth, B., Duncker, H. et al. All-optical preparation of molecular ions in the rovibrational ground state. Nature Phys 6, 275–278 (2010). https://doi.org/10.1038/nphys1605

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