Accurate Charge Radius Measurement of 14C Confronts Ab Initio Theory
Abstract
Located at the neutron shell closure N = 8, the long-lived radioactive isotope 14C plays a critical role in geochronology and nuclear structure studies. Despite its widespread use, the nuclear charge radius of 14C has remained less precisely known compared to its stable counterpart 12C. Here, we report a high-precision determination of the 14C charge radius using collinear laser spectroscopy at the COALA setup at TU Darmstadt, improving upon the precision of previous muonic measurements by a factor $5$ and revealing a 1.9σ discrepancy of combined uncertainty, indicating a likely underestimated uncertainty in the muonic determination. This measurement challenges state-of-the-art ab initio nuclear theory calculations, including auxiliary field diffusion Monte Carlo, the valence-space in-medium similarity renormalization group, and the no-core shell model, augmented by neural-network techniques. With 12C and 14C now forming one of the most precisely characterized even-even isotope pairs, these results also enable improved QED tests.
Versions
Related
- Accurate ab initio calculations of the ground state properties of singly charged alkali metal hydrides
- Universal Interatomic Potentials as Configuration-Space Generators for One-Shot and Iterative Fine-Tuning of Ab Initio-Accurate Material-Specific Models
- Nuclear moments, charge radii, and magnetization distribution parameters of Ag isotopes from laser spectroscopy and \textit{ab initio} electronic-structure calculations
- Sensitivity of the photon-induced processes to the proton charge radius
- Implications of exclusive photon leptoproduction measurements for the proton charge-radius puzzle
BibTeX
@misc{konig2026accurate,
title = {{Accurate Charge Radius Measurement of $^14$C Confronts Ab Initio Theory}},
author = {Kristian König and Patrick Müller and Tobias Gesser and Emily Burbach and Stefano Gandolfi and Matthias Heinz and Phillip Imgram and Alessandro Lovato and Pieter Maris and Takayuki Miyagi and Wilfried Nörtershäuser and Robert Roth and Julien Spahn and Achim Schwenk},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.17052},
eprint = {2608.17052},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.17052},
}
RIS
TY - UNPB
TI - Accurate Charge Radius Measurement of ^14C Confronts Ab Initio Theory
AU - Kristian König
AU - Patrick Müller
AU - Tobias Gesser
AU - Emily Burbach
AU - Stefano Gandolfi
AU - Matthias Heinz
AU - Phillip Imgram
AU - Alessandro Lovato
AU - Pieter Maris
AU - Takayuki Miyagi
AU - Wilfried Nörtershäuser
AU - Robert Roth
AU - Julien Spahn
AU - Achim Schwenk
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2608.17052
UR - https://arxiv.org/abs/2608.17052
AB - Located at the neutron shell closure N = 8, the long-lived radioactive isotope ^14C plays a critical role in geochronology and nuclear structure studies. Despite its widespread use, the nuclear charge radius of ^14C has remained less precisely known compared to its stable counterpart ^12C. Here, we report a high-precision determination of the ^14C charge radius using collinear laser spectroscopy at the COALA setup at TU Darmstadt, improving upon the precision of previous muonic measurements by a factor $5$ and revealing a 1.9σ discrepancy of combined uncertainty, indicating a likely underestimated uncertainty in the muonic determination. This measurement challenges state-of-the-art ab initio nuclear theory calculations, including auxiliary field diffusion Monte Carlo, the valence-space in-medium similarity renormalization group, and the no-core shell model, augmented by neural-network techniques. With ^12C and ^14C now forming one of the most precisely characterized even-even isotope pairs, these results also enable improved QED tests.
ER -