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Trapped Ions

by Sebastien_Tanzilli - published on , updated on

Main contact: Laurent Hilico
Other contacts: Jean-Philippe Karr
Albane Douillet

Research activities:

Experimental activity
We have set up an experiment for two-photon vibrational spectroscopy of the hydrogen molecular ion, which aims at a new determination of the proton-to-electron, with a relative uncertainty in the 0.1 ppb range. The vibrational transition will be detected by Resonance Enhanced Multi-Photon Dissociation (REMPD).
The experimental setup consists of

  • a radiofrequency Paul trap confining a cloud of H2+ ions.
  • a quantum cascade laser (QCL) for excitation of the two-photon transition.
  • an excimer laser at 248 nm for selective photodissociation.

Theoretical activity
Our theoretical activity is mainly aimed to support the experimental project. We have developed numerical codes for high-accuracy variational calculations of nonrelativistic energies and wave functions of three-body systems. In collaboration with V. Korobov, we calculate relativsitic, radiative and hyperfine structure corrections to the energy levels of H2+. We have also started the evaluation of systematic effects (such as Zeeman or Stark effects) affecting vibrational transition frequencies.


  • Development of a linear quadrupole trap, in order to allow for a tighter focusing of the laser beam.
  • Production of H2+ ions in selected ro-vibrational states by Resonance Enhanced Multi-Photo Ionization (REMPI) at 3 or 4 photons.
  • High-frequency modulation (up to 10 GHz) of quantum cascade lasers.
  • Trapping and cooling of 9Be+ or 24Mg+ ions.
  • Sympathetic cooling of H2+ by 9Be+ or 24Mg+.
  • Calculation of radiative corrections of order to the ro-vibrational energy levels of H2+.
  • Evaluation of the second-order Doppler effect.

For more information: see online Trapped Ions @ LKB