CoulEx Measurement of Octupole Collectivity in {224,226}Th
Name
PTMMurthy_Th224-226_FRIB-GRETA-ChicoX_Ver2-Preprint.pdf
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1.21 MB
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Adobe PDF
Checksum (MD5)
812e906084c6540cd1698a693f87aff7
Author(s)
Mohanmurthy, Prajwal
Winger, Jeff A.
Thenabadu, Rairu
Griffth, Mila
Crider, Benjamin
Ayangeakaa, Akaa D.
Date Issued
September 9, 2026
Abstract
Octupole deformation can strongly enhance nuclear Schiff moments and thereby the sensitivity of atomic and molecular based searches to hadronic CP violation. Of particular interest is 229Pa, where octupole and quadrupole deformation and a possible low-lying parity doublet enhance its nuclear Schiff moment significantly. A reliable characterization of its collective nuclear structure requires experimental constraints from the neighboring even-even Thorium isotopes, which provide the underlying collective cores for odd-A Thorium and Protactinium nuclei. While octupole collectivity has been mapped systematically in neighboring Radium and Radon isotopic chains, its onset, maximum, and disappearance across the even-even Thorium chain remain poorly constrained. We therefore propose Coulomb-excitation (CoulEx) measurements of the short-lived {224,226}Th isotopes at FRIB using radioactive beams incident at 3 MeV/u on a stable 120Sn target of thickness 2 mg/cm^2. Scattered beam and target-recoil ions will be measured with CHICO-X in coincidence with prompt gamma-rays detected by GRETA. The experiment will determine the E1 and E3 transition strengths from the low-lying states, with the well-known E2 strength providing an internal normalization. The primary goal is to constrain octupole collectivity through the E3 matrix elements and, with substantially greater statistics, through the E1 strengths. Together with existing measurements in heavier Thorium isotopes (and complementary planned measurements in {220,222}Th) these measurements will establish the evolution of octupole collectivity across the entire Thorium isotopic chain spanning the octupole deformation island. These measurements will also provide essential nuclear-structure input for interpreting measurements involving not only 229Pa but also other neighboring odd-A nuclei relevant to enhanced EDM and nuclear-Schiff-moment searches, like 227Th. We request a total of 5.5 days of beam time for the combined {224,226}Th CoulEx measurements.
Abstract footnote comment: This work is supported by Phi Kappa Phi and Oak Ridge Associated Universities Fellowships, and generous support from Prof. R. P. Redwine.
Subjects
Atomic EDm
Nuclear Structure
Nuclear Spectroscopy
Thorium isotopes
Coulomb Excitation
FRIB
GRETA
CHICO-X
MIT Department
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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