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Reference : UMR8552-LAUHIL-003
Workplace : PARIS 05
Date of publication : Friday, July 31, 2020
Scientific Responsible name : Laurent Hilico
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Improving fundamental constants: Doppler free two-photon transition in H2+ for proton to electron mass ratio determination
The electron to proton mass ratio me/mp is a fundamental constant known today with a relative uncertainty of 4.3 10-11 from unique and independent measurements of me and mp in Penning trap. Direct optical determination of this constant can be done by spectroscopy of the H2+ molecular ion because the vibration frequency of the nuclei of this ion depends essentially on me/mp. Recent theoretical advances in the calculation of H2+ transition frequencies, including relativistic, radiative and hyperfine structure corrections together with the development of a dedicated Doppler-free two-photon spectroscopy experiment on state selected trapped and sympathetically cooled H2+ ions, should improve the uncertainty on me/mp by a factor of 3 - and even 6 in the long term. Comparison with similar measurements made on the HD+ ion in Düsseldorf and Amsterdam will not only improve the knowledge of me/mp, but also provide a "molecular" determination of the Rydberg constant and the charge radius of the proton, providing new insights into the proton size puzzle.
An experimental setup has been recently achieved and is ready for data taking. The student and then PhD work will be focused on
• Implementation of an optical frequency comb and non-linear mixings for frequency control of the quantum cascade laser used for spectroscopy
• Optimisation of state selected H2+ ion production
• Observation of a Doppler free two-photon transition
• Analysis of systematic effects and optical determination of the proton to electron mass ratio
Work in the frame of the trapped ion team at LKB.
Constraints and risks
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