Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii

The discrepancy in the squared nuclear charge radius difference, ΔR^{2}, between ^{3}He and ^{4}He, as determined from electronic and muonic atom energy levels, presents an unresolved puzzle. This paper shows that accounting for off-diagonal hyperfine mixing effects can substantially reduce this dis...

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Main Authors: Xiao-Qiu Qi, Pei-Pei Zhang, Zong-Chao Yan, Li-Yan Tang, Ai-Xi Chen, Ting-Yun Shi, Zhen-Xiang Zhong
Format: Article
Language:English
Published: American Physical Society 2025-04-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.7.L022020
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author Xiao-Qiu Qi
Pei-Pei Zhang
Zong-Chao Yan
Li-Yan Tang
Ai-Xi Chen
Ting-Yun Shi
Zhen-Xiang Zhong
author_facet Xiao-Qiu Qi
Pei-Pei Zhang
Zong-Chao Yan
Li-Yan Tang
Ai-Xi Chen
Ting-Yun Shi
Zhen-Xiang Zhong
author_sort Xiao-Qiu Qi
collection DOAJ
description The discrepancy in the squared nuclear charge radius difference, ΔR^{2}, between ^{3}He and ^{4}He, as determined from electronic and muonic atom energy levels, presents an unresolved puzzle. This paper shows that accounting for off-diagonal hyperfine mixing effects can substantially reduce this discrepancy. We find that hyperfine mixing with the n^{3}S and n^{1}S states (n>2) in ^{3}He introduces a correction of −1.37 kHz to the isotope shift of the 2^{1}S−2^{3}S transition, a factor of seven times larger than the current uncertainty. This correction modifies ΔR^{2} by −0.0064fm^{2}, shifting it from 1.0757(15)fm^{2} to 1.0693(15)fm^{2}, as initially reported by Werf et al. [arXiv:2306.02333]. This brings ΔR^{2} closer to the value of 1.0636(31)fm^{2} obtained from muonic helium μHe^{+} by Schuhmann et al. [arXiv:2305.11679], narrowing the existing discrepancy from 3.6σ to 1.7σ. The adjusted value ΔR^{2} also agrees well with the result of 1.069(3) fm^{2} derived from the helium 2^{3}S−2^{3}P transitions, as analyzed by Patkóš et al. [Phys. Rev. A 94, 052508 (2016)10.1103/PhysRevA.94.052508]. Our results provide key insights for resolving the discrepancy in ΔR^{2}.
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spelling doaj-art-b67e1e90200747d0867dc14c790f64dc2025-08-20T03:18:27ZengAmerican Physical SocietyPhysical Review Research2643-15642025-04-0172L02202010.1103/PhysRevResearch.7.L022020Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radiiXiao-Qiu QiPei-Pei ZhangZong-Chao YanLi-Yan TangAi-Xi ChenTing-Yun ShiZhen-Xiang ZhongThe discrepancy in the squared nuclear charge radius difference, ΔR^{2}, between ^{3}He and ^{4}He, as determined from electronic and muonic atom energy levels, presents an unresolved puzzle. This paper shows that accounting for off-diagonal hyperfine mixing effects can substantially reduce this discrepancy. We find that hyperfine mixing with the n^{3}S and n^{1}S states (n>2) in ^{3}He introduces a correction of −1.37 kHz to the isotope shift of the 2^{1}S−2^{3}S transition, a factor of seven times larger than the current uncertainty. This correction modifies ΔR^{2} by −0.0064fm^{2}, shifting it from 1.0757(15)fm^{2} to 1.0693(15)fm^{2}, as initially reported by Werf et al. [arXiv:2306.02333]. This brings ΔR^{2} closer to the value of 1.0636(31)fm^{2} obtained from muonic helium μHe^{+} by Schuhmann et al. [arXiv:2305.11679], narrowing the existing discrepancy from 3.6σ to 1.7σ. The adjusted value ΔR^{2} also agrees well with the result of 1.069(3) fm^{2} derived from the helium 2^{3}S−2^{3}P transitions, as analyzed by Patkóš et al. [Phys. Rev. A 94, 052508 (2016)10.1103/PhysRevA.94.052508]. Our results provide key insights for resolving the discrepancy in ΔR^{2}.http://doi.org/10.1103/PhysRevResearch.7.L022020
spellingShingle Xiao-Qiu Qi
Pei-Pei Zhang
Zong-Chao Yan
Li-Yan Tang
Ai-Xi Chen
Ting-Yun Shi
Zhen-Xiang Zhong
Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
Physical Review Research
title Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
title_full Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
title_fullStr Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
title_full_unstemmed Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
title_short Toward resolving the discrepancy in helium-3 and helium-4 nuclear charge radii
title_sort toward resolving the discrepancy in helium 3 and helium 4 nuclear charge radii
url http://doi.org/10.1103/PhysRevResearch.7.L022020
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