Search for the 229Pa Parity Doublet via Internal-Conversion Spectroscopy at FRIB
Abstract
The radioisotope 229Pa is predicted to possess a nearly degenerate ground-state parity doublet. Previous γ-ray and conversion-electron spectroscopy suggests a splitting of ΔE = (60± 50) eV, although the doublet's existence remains unconfirmed. Such a small splitting would give 229Pa an exceptionally large enhancement of symmetry-violating nuclear properties. However, the splitting, and with it the sensitivity of 229Pa to CP-violating physics, remains uncertain by orders of magnitude. We propose an experiment to measure this splitting with sub-eV precision within a few days of measurement time by using delayed-coincidence internal-conversion spectroscopy of 229Pa ions produced by the electron-capture decay of 229U+ ions stored in a Penning trap at the Facility for Rare Isotope Beams (FRIB). This measurement would provide the key nuclear-structure input needed to establish 229Pa as a leading candidate for next-generation atomic and molecular electric-dipole-moment (EDM) experiments.
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BibTeX
@misc{udrescu2026search,
title = {{Search for the 229Pa Parity Doublet via Internal-Conversion Spectroscopy at FRIB}},
author = {Silviu-Marian Udrescu and Aiden Boyer and Lan Cheng and Ronald Fernando Garcia Ruiz and Phay J. Ho and Ryan Ringle and Jaideep T. Singh and Patrick R. Stollenwerk and Georg Tiebel and Margaret J. Tseng},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05494},
eprint = {2611.05494},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05494},
}
RIS
TY - UNPB
TI - Search for the 229Pa Parity Doublet via Internal-Conversion Spectroscopy at FRIB
AU - Silviu-Marian Udrescu
AU - Aiden Boyer
AU - Lan Cheng
AU - Ronald Fernando Garcia Ruiz
AU - Phay J. Ho
AU - Ryan Ringle
AU - Jaideep T. Singh
AU - Patrick R. Stollenwerk
AU - Georg Tiebel
AU - Margaret J. Tseng
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05494
UR - https://arxiv.org/abs/2611.05494
AB - The radioisotope ^229Pa is predicted to possess a nearly degenerate ground-state parity doublet. Previous γ-ray and conversion-electron spectroscopy suggests a splitting of ΔE = (60± 50) eV, although the doublet's existence remains unconfirmed. Such a small splitting would give ^229Pa an exceptionally large enhancement of symmetry-violating nuclear properties. However, the splitting, and with it the sensitivity of ^229Pa to CP-violating physics, remains uncertain by orders of magnitude. We propose an experiment to measure this splitting with sub-eV precision within a few days of measurement time by using delayed-coincidence internal-conversion spectroscopy of ^229Pa ions produced by the electron-capture decay of ^229U^+ ions stored in a Penning trap at the Facility for Rare Isotope Beams (FRIB). This measurement would provide the key nuclear-structure input needed to establish ^229Pa as a leading candidate for next-generation atomic and molecular electric-dipole-moment (EDM) experiments.
ER -