Jean-Philippe Karr

Theoretical Hyperfine Structure of the Molecular Hydrogen Ion at the 1 ppm Level.

We revisit the mα^{6}(m/M) order corrections to the hyperfine splitting in the H_{2}^{+} ion and find a hitherto unrecognized second-order relativistic contribution associated with the vibrational motion of the nuclei. Inclusion of this correction term produces theoretical predictions which are in excellent agreement with experimental data [K. B. Jefferts, Phys. Rev. Lett. 23, 1476 (1969)], thereby concluding a nearly 50-year-long theoretical quest to explain the experimental results within their 1-ppm error. The agreement between the theory and experiment corroborates the proton structural properties as derived from the hyperfine structure of atomic hydrogen. Our work furthermore indicates that, for future improvements, a full three-body evaluation of the mα^{6}(m/M) correction term will be mandatory.

Why three-body physics does not solve the proton-radius puzzle.

The possible involvement of weakly bound three-body systems in the muonic hydrogen spectroscopy experiment, which could resolve the current discrepancy between determinations of the proton radius, is investigated. Using variational calculations with complex coordinate rotation, we show that in the pμe ion, which was recently proposed as a possible candidate, the pμ core fails to bind the outer electron tightly enough to explain the discrepancy. It is also shown that the ppμ molecular ion cannot play any role in the observed line.

Two-photon spectroscopy of trapped HD+ ions in the Lamb-Dicke regime

We study the feasibility of nearly-degenerate two-photon rovibrational spectroscopy in ensembles of trapped, sympathetically cooled hydrogen molecular ions using a resonance-enhanced multiphoton dissociation (REMPD) scheme. Taking advantage of quasi-coincidences in the rovibrational spectrum, the excitation lasers are tuned close to an intermediate level to resonantly enhance two-photon absorption. Realistic simulations of the REMPD signal are obtained using a four-level model that takes into account saturation effects, ion trajectories, laser frequency noise and redistribution of population by blackbody radiation. We show that the use of counterpropagating laser beams enables optical excitation in an effective Lamb-Dicke regime. Sub-Doppler lines having widths in the 100 Hz range can be observed with good signal-to-noise ratio for an optimal choice of laser detunings. Our results indicate the feasibility of molecular spectroscopy at the

Preparing single ultra-cold antihydrogen atoms for free-fall in GBAR

10^{-14}

Cross-damping effects in 1S−3S spectroscopy of hydrogen and deuterium

accuracy level for improved tests of molecular QED, a new determination of the proton-to-electron mass ratio, and studies of the time (in)dependence of the latter.

Hydrogen molecular ions: new schemes for metrology and fundamental physics tests

We discuss an experimental approach allowing to prepare antihydrogen atoms for the GBAR experiment. We study the feasibility of all necessary experimental steps: The capture of incoming

Note: A high transmission Faraday optical isolator in the 9.2 μm range

\bar{\rm H}^+

\(\bar{\text{H}}^{+}\) Sympathetic Cooling Simulations with a Variable Time Step

ions at keV energies in a deep linear RF trap, sympathetic cooling by laser cooled Be

Towards a test of the weak equivalence principle of gravity using anti-hydrogen at CERN

^+

Resonances in two-electron atoms below the critical charge

ions, transfer to a miniaturized trap and Raman sideband cooling of an ion pair to the motional ground state, and further reducing the momentum of the wavepacket by adiabatic opening of the trap. For each step, we point out the experimental challenges and discuss the efficiency and characteristic times, showing that capture and cooling are possible within a few seconds.