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Felix Schneider (TU Wien)18/05/2026, 17:40Poster
The lowest-energy Thorium-229 isomeric state at 148.3 nm can be used to build a worlds-first nuclear clock. The transition is also sensitive to variations of the fine-structure constant and may be used to search for dark matter.
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This poster presents the ongoing experimental progress towards building and optimizing a continuous-wave laser system at 148.38 nm and its use in high-precision... -
Iren Ignatov (Technion - Israel Institute of Technology)18/05/2026, 17:41Poster
Muonium is an exotic atom consisting of a positive muon and an electron. As it comprises two leptons, it lacks contributions from hadronic interactions or corrections due to the finite size of the nucleus, while still resembling hydrogen in its theoretical simplicity. Therefore, comparing measured and calculated energy levels in muonium provides a clean test of QED. Here, I report a new...
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Patrick Schaile (Max-Planck-Institut für Quantenoptik)18/05/2026, 17:42Poster
Precision spectroscopy of atomic hydrogen provides a uniquely clean test of bound-state quantum electrodynamics due to its simple electronic structure. While spectroscopy of trapped atomic samples can significantly enhance precision, trapping hydrogen in optical potentials has not been realized yet. Existing approaches rely on magnetic trapping, which introduce substantial Zeeman shifts and...
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Dr Ádám Margócsy (ELTE, Eötvös Loránd University)18/05/2026, 17:47Poster
Spectroscopists have been interested in the low-lying electronically excited states of $\text{He}_2$ (the lowest being $^3\Sigma_\text{u}^+$, denoted as "a") and their cation (ground state $^2\Sigma_\text{u}^+$, denoted as "X") for decades. These excited states are strongly bound compared to the $^1\Sigma_\text{g}^+$ ground state and, therefore, have much richer rovibrational spectra. The...
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Mr Mathis Panet (Laboratoire Kastler Brossel - Sorbonne Universite)18/05/2026, 17:48Poster
In the last decade, the experimental determination of the transition frequencies of Molecular Hydrogen Ions (MHIs) has improved significantly, reaching a level of precision that surpasses theoretical predictions. These advances play a crucial role in the determination of fundamental constants (e.g., $m_p/m_e$) and the testing of the Standard Model [1]. However, they also highlight the need for...
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Fabian Raab18/05/2026, 17:49Poster
LSym is a new cryogenic Penning trap experiment that intends to test the
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symmetry of matter and antimatter in the lepton sector. By measuring the coherent difference of their spin precession, the experiment will test for differences in mass, charge and g-factor of the positron and electron to achieve the most precise test for a hypothetical CPT violation for leptons so far. In the experiment... -
Prof. Michael Eides (University of Kentucky)18/05/2026, 17:50Poster
Uncertainty of the quantum electrodynamics theoretical prediction for the hyperfine splitting in the ground state of muonium is considered. It is compared with the respective discussion in the two most recent CODATA adjustments of the fundamental physical constants.
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Vadim Lensky (JGU Mainz)18/05/2026, 17:51Poster
We evaluate the hadronic vacuum polarization corrections to the Lamb shift and hyperfine splitting of $1S$ and $2S$ energy levels in ordinary and muonic hydrogen as well as ${}^3\mathrm{He}^+$ ions. Despite the smallness of these corrections, their precise knowledge is very important in view of the high experimental precision achieved in measurements of the spectra of both ordinary and muonic...
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95. Wichmann-Kroll vacuum polarization correction to lithium-like systems \\ in a Gaussian basis setHaisum Hayat (University of Melbourne)18/05/2026, 17:52Poster
Recent developments have seen the application of finite Gaussian basis sets to the $\alpha(Z\alpha)^{n\geq3}$ vacuum polarization. The energy shift for $s$ and $p$ electron states have been tabulated and their convergence investigated. In this work, we extend this problem to the multi-electron case. Hartee-Fock potentials obtained self-consistently are used to treat the vacuum polarization for...
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Joanna Peszka (GSI Helmholtz Centre for Heavy Ion Research)18/05/2026, 17:53Poster
Low-energy beams of positive muons, at tens of keV and below, allow for experiments in the field of fundamental particle physics, such as the search for the muon electric dipole moment [1], exotic atoms physics with muonium spectroscopy and gravitational experiments [2] and numerous material science applications thanks to muon-spin resonance (muSR) technique [3]. Current sources of muons...
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Katharina Schreiner (Laboratoire Kastler Brossel / Marietta Blau Institute)18/05/2026, 17:54Poster
If a sufficiently slow beam of particles is incident upon a curved surface with a small grazing angle, so called whispering gallery states (WGS) will form. The WGS are quasi-stable quantum states, arising from the effect of the centrifugal force and mirror surface potentials experienced by the particles. Interference patterns generated by WGS have already been measured with cold neutrons at...
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Martin Simon (Austrian Academy of Sciences (AT))18/05/2026, 17:55Poster
Hyperfine structure measurements on antihydrogen can provide sensitive tests of CPT invariance. The ASACUSA collaboration proposed such experiments on a beam of antihydrogen at the antiproton decelerator of CERN. We benchmark spectroscopy methods and equipment in supporting matter experiments. Beyond the relevance for antihydrogen these measurements can put new as well as improved constraints...
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Tymon Kilich (University of Warsaw)18/05/2026, 17:56Poster
The hydrogen anion H$^-$ is the lightest stable anion and its bound states and resonances are well studied, but magnetic shielding has not been computed to comparable precision. Due to the planned comparison of the bare antiproton to H$^-$ in a Penning trap, we study the magnetic shielding of H$^-$ using nonrelativistic quantum electrodynamics theory (NRQED). We compute the nonrelativistic...
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Péter Jeszenszki (MTA–ELTE Lendület ‘Momentum’ Molecular Quantum electro-Dynamics Research Group, Institute of Chemistry, Eötvös Loránd University, Pázmány Péter sétány 1/A, Budapest, H-1117, Hungary)18/05/2026, 17:57Poster
The simplest, algebraic quantum-electrodynamical corrections due to the double-negative energy subspace and instantaneous interactions are computed to the no-pair energy of two-spin-1/2-fermion systems$^1$. Numerical results are reported for two-electron atoms with a clamped nucleus and positronium-like genuine two-particle systems. The Bethe-Salpeter equation provides the theoretical...
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Quentin Senetaire (Laboratoire Kastler Brossel (FR))18/05/2026, 17:58Poster
Precision measurements to study strong-field Bound-State Quantum Electrodynamics (BSQED) involve systems that remain largely unexplored, and thus requires the use of new detection techniques. One paradigm lies in the spectroscopy of transitions between Rydberg states of exotic atoms [1].
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The antiProtonic Atom X-ray spectroscopy (PAX) experiment aims to study such transitions in mid to high-Z... -
Balázs Rácsai (MTA–ELTE Lendület ‘Momentum’ Molecular Quantum electro-Dynamics Research Group, Institute of Chemistry, Eötvös Loránd University, Pázmány Péter sétány 1/A, Budapest, H-1117, Hungary)18/05/2026, 17:59Poster
Relativistic, quantum electrodynamics, as well as non-adiabatic corrections and couplings, are computed for the $\text{b}\ ^3\Pi_\text{g}$ and $\text{c}\ ^3\Sigma_\text{g}^+$ electronic states of the helium dimer. The underlying Born-Oppenheimer potential energy curves are converged to 1 ppm ($1:10^6$) relative precision using a variational explicitly correlated Gaussian approach. The quantum...
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Dimitar Bakalov (INRNE)18/05/2026, 18:00Poster
We determine from the available experimental data the cross section of muon transfer to molecular oxygen at low energies with account of the oxygen molecule structure. Building on an earlier work, the results highlight the role of the molecular structure effects and significantly improve the agreement with theoretical calculations of the muon transfer rate. An efficient computational model of...
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Maria Beatriz Gomes Goncalves (Swansea University (GB))18/05/2026, 18:01Poster
Antihydrogen, the bound state of a positron and an antiproton, is a uniquely powerful system for precision tests of fundamental symmetries between matter and antimatter. The ALPHA collaboration synthesises antihydrogen by merging cold positron and antiproton plasmas. The positron temperature limits the number of trapped antihydrogen atoms, thereby constraining the data-taking rate and...
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Xiao-Qiu Qi (Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China)18/05/2026, 18:02Poster
We report recent progress in precision spectroscopy of helium isotopes ($^{3,4}$He) and lithium ions ($^{6,7}$Li$^+$), focusing on extracting nuclear structure information from high-accuracy atomic transitions. For helium, we consider the off-diagonal hyperfine mixing effects to resolve the discrepancy in the squared charge-radius difference between $^3$He and $^4$He, leading to a new squared...
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Goncalo Garces Sobreira Rodrigues Baptista (Laboratoire Kastler Brossel (FR))18/05/2026, 18:03Poster
The PAX experiment is a new effort to improve the study of x ray transitions in antiprotonic atoms for testing Bound State QED (BSQED) [1,2]. By selecting transitions between circular Rydberg states, where the bound antiproton resides orders of magnitude closer to the nucleus than an electron, whilst avoiding any nuclear overlap with its wavefunction, the dominant uncertainties that limit the...
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Vitaly Wirthl (MPQ)18/05/2026, 18:04Poster
Our recent measurement of the 2S–6P transition frequency in atomic hydrogen [1] achieves a precision of 0.7 parts per trillion, enabling a Standard Model (SM) test at a level comparable to the electron anomalous magnetic moment (g−2) [2] and representing the most precise test to date of bound-state quantum electrodynamics (QED) to 0.5 parts per million. This poster presents our ongoing efforts...
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Lei Cong (Helmholtz Institute Mainz)18/05/2026, 18:05Poster
Precision atomic spectroscopy provides a sensitive probe of physics beyond the Standard Model. A recently reported theory-experiment discrepancy in the ionization energy of metastable helium has motivated the hypothesis of a new boson mediating exotic electron-electron interactions. Using a model-independent sign-consistency analysis of the induced energy shifts, we show that the sign...
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Daniel Mayer (Acceleron Fusion, Inc.)18/05/2026, 18:06Poster
In hydrogen isotopic mixtures, stopped muons form tightly bound exotic molecules in which nuclear fusion proceeds rapidly, as the muon’s large mass enhances Coulomb barrier penetration between the nuclei. Following fusion, the muon is typically released and can repeat the process until it decays or becomes stuck to a final-state helium nucleus, with over 100 fusions per muon having been...
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Ayodeji Awobode (Department of Physics, University of Massachusetts, Boston, Massachusetts, USA)18/05/2026, 18:07Poster
Deviations from the exact value 1, of the electron orbital g-factor g_L, are determined from the measured g_J ratios of some states of the noble gas atoms He, Ne and Ar. The calculated values are compared with those previously found from the ratio of the Lande g-factors measured on the atoms of In, Ga and Na. The anomalies obtained from some of the rare gas atoms are, at least, one order of...
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