English

Nuclear Charge Radius of $^9$Be from Muonic Atom Spectroscopy Using a Microcalorimeter

Nuclear Experiment 2026-07-15 v1 Nuclear Theory Atomic Physics
Authors: Ofir Eizenberg , Shikha Rathi , Andreas Abeln , Sonia Bacca , Gonçalo Baptista , Nir Barnea , Noam Burger , Thomas Elias Cocolios , Marie Deseyn , Tim Egert , Christian Enss , Andreas Fleischmann , Loredana Gastaldo , César Godinho , Nitzan Goldberg , Michael Heines , Daniel Hengstler , Paul Indelicato , Weiguang Jiang , Klaus Kirch , Andreas Knecht , Daniel Kreuzberger , Jorge Machado , Ulf-G. Meißner , Ben Ohayon , Nancy Paul , Randolf Pohl , Tim Redelbach , Michael Roosa , Katharina von Schoeler , Quentin Senetaire , Shihang Shen , Daniel Unger , Stergiani Marina Vogiatzi , Johanna Walch , Frederik Wauters , Aziza Zendour
View on arXiv ↗ PDF ↗

Abstract

The 2p→1s2p\to1s transition energy in muonic 9^9Be was measured using a metallic magnetic calorimeter, resulting in E2p→1s=33 391.48(34) E_{2p\to 1s}=33\,391.48(34)\,eV. The result is 30 times more precise than the previous best measurement and enables the extraction of the corresponding nuclear charge radius rc(r_c(9^9Be)=2.5506(51) )=2.5506(51)\,fm. It is 2.42.4 times more precise than the commonly used value based on electron scattering and differs from it by 2.32.3 times the combined uncertainties. This measurement represents the first determination of a nuclear charge radius using muonic x-ray spectroscopy with microcalorimeters.

Keywords

nuclear charge radius muonic atom spectroscopy microcalorimeter Beryllium-9 metallic magnetic calorimeter X-ray spectroscopy

Cite

@article{arxiv.2607.13690,
  title  = {Nuclear Charge Radius of $^9$Be from Muonic Atom Spectroscopy Using a Microcalorimeter},
  author = {Ofir Eizenberg and Shikha Rathi and Andreas Abeln and Sonia Bacca and Gonçalo Baptista and Nir Barnea and Noam Burger and Thomas Elias Cocolios and Marie Deseyn and Tim Egert and Christian Enss and Andreas Fleischmann and Loredana Gastaldo and César Godinho and Nitzan Goldberg and Michael Heines and Daniel Hengstler and Paul Indelicato and Weiguang Jiang and Klaus Kirch and Andreas Knecht and Daniel Kreuzberger and Jorge Machado and Ulf-G. Meißner and Ben Ohayon and Nancy Paul and Randolf Pohl and Tim Redelbach and Michael Roosa and Katharina von Schoeler and Quentin Senetaire and Shihang Shen and Daniel Unger and Stergiani Marina Vogiatzi and Johanna Walch and Frederik Wauters and Aziza Zendour},
  journal= {arXiv preprint arXiv:2607.13690},
  year   = {2026}
}