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Population distribution of product states following three-body recombination in an ultracold atomic gas


Three-body recombination is a collision process where two atoms combine to form a molecule and a third atom carries away part of the released reaction energy. Here, we experimentally determine for the first time the population distribution of the molecular reaction products after a three-body recombination for non-resonant particle interactions. The key to our measurements is a sensitive detection scheme that combines the photoionization of the molecules with subsequent ion trapping. Using an ultracold 87Rb gas at very low kinetic energy below h×20 kHz, we find a broad population of final states with binding energies of up to h×750 GHz. This is in contrast with previous experiments, performed in the resonant interaction regime, that found a dominant population of only the most weakly bound molecular state or the occurrence of Efimov resonances. This work may contribute to the development of an in-depth model that can qualitatively and quantitatively predict the reaction products of three-body recombination.

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Figure 1: Illustration of recombination and ionization in the atom–ion trap.
Figure 2: Dependence of the ion production rate Γion on atomic density.
Figure 3: REMPI spectrum.
Figure 4: Dependence of the ion production rate on the intensity of the dipole trap laser.
Figure 5: Overview over relevant molecular levels and transitions.


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The authors would like to thank S. Schmid and A. Brunner for support during early stages of the experiment and O. Dulieu, B. Esry, J. d’Incao, W. Stwalley, U. Heinzmann, J. Hutson, P. Soldan, T. Bergeman and A. Drozdova for valuable information and fruitful discussions. This work was supported by the German Research Foundation DFG within the SFB/TRR21.

Author information




A.H. and A.K. performed the experiments in the atom–ion trap set-up; M.D. and B.D. performed spectroscopic measurements on Rb2 molecules; A.H., A.K., E.T. and J.H.D. analysed data; A.H., E.T. and J.H.D. wrote the paper.

Corresponding author

Correspondence to J. Hecker Denschlag.

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The authors declare no competing financial interests.

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Härter, A., Krükow, A., Deiß, M. et al. Population distribution of product states following three-body recombination in an ultracold atomic gas. Nature Phys 9, 512–517 (2013).

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