Studies of pear-shaped nuclei using accelerated radioactive beams

Area of Science:

• Nuclear Physics
• Atomic Physics

Background:

• Atomic nuclei typically exhibit quadrupole deformation (rugby-ball shape).
• Octupole deformation (pear shape) in nuclei is theoretically significant but experimentally elusive.
• Octupole deformed nuclei are crucial for understanding nuclear structure and searching for physics beyond the Standard Model, as they can amplify electric-dipole moments.

Purpose of the Study:

• To experimentally determine electric octupole transition strengths, a direct measure of octupole correlations.
• To investigate octupole deformation in short-lived isotopes of radon and radium.
• To differentiate between theoretical models of octupole correlations and identify candidates for electric-dipole moment searches.

Main Methods:

• Performed Coulomb excitation experiments using accelerated beams of heavy, radioactive ions.
• Measured electric octupole transition strengths for isotopes (220)Rn and (224)Ra.
• Analyzed experimental data to assess the degree of octupole deformation.

Main Results:

• Provided clear evidence for stronger octupole deformation in (224)Ra compared to (220)Rn.
• Quantified octupole transition strengths, offering direct insights into octupole correlations.
• The findings support the existence and significance of octupole deformed nuclei.

Conclusions:

• The experimental data enable discrimination between competing theoretical approaches to nuclear octupole correlations.
• The results help identify suitable candidates for future experiments searching for atomic electric-dipole moments.
• This research advances the understanding of nuclear structure and the potential for discovering new physics beyond the Standard Model.