Speaker
Description
Light heliumlike systems are ideal cases to benchmark state of the art atomic and nuclear theory as their nuclei exhibit interesting cluster and halo structures and their atomic structure is accessible for high-precision ab initio calculations. With recent progress in nonrelativistic quantum electrodynamics (NRQED) calculations [1], even an all-optical extraction of absolute nuclear charge radii from light heliumlike systems became possible. In an ongoing effort, we therefore plan to determine absolute and differential nuclear charge radii, $R_\mathrm{C}$ and $\delta\!R_\mathrm{C}$, of the light elements Be to N by purely using collinear laser spectroscopy (CLS) and ab initio NRQED calculations. As a first step, we measured the absolute transition frequencies of the $1s2s\,^3\mathrm{S}_1\rightarrow 1s2p\,^3\mathrm{P}_J$ lines of $^{12,13}\mathrm{C}^{4+}$ at the ppb precision level using the Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA) at the Technical University of Darmstadt.
We present two prospects of our latest results: The use of the $^3$P$_J$ frequency splittings to identify the dominant terms in the next order ($m\alpha^8$) of the power expansion of the NRQED calculations and the determination of $R_\mathrm{C}^{12}$ as well as $\delta\!R_\mathrm{C}^{12,13}$ to benchmark ab initio nuclear structure calculations [2]. Particularly, the analysis of $^{13}\mathrm{C}^{4+}$, which is modulated by significant hyperfine-induced mixing, poses an additional challenge. Our nuclear model-independent charge radii are compared to new in-medium similarity renormalization group (IMSRG) and no-core shell model (NCSM) calculations as well as existing results from elastic electron scattering and muonic atom spectroscopy. Future plans and perspectives on how to extend the CLS measurements to heliumlike Be, B and N are outlined.
This project is supported by DFG (Project-ID 279384907 - SFB 1245).
[1] V. A. Yerokhin et al., Phys. Rev. A 106, 022815 (2022)
[2] P. Imgram et al., Phys. Rev. Lett. 131, 243001 (2023)
