Charge Radii of Neutron Deficient ^{52,53}Fe Produced by Projectile Fragmentation.

Area of Science:

• Nuclear Physics
• Atomic Physics
• Laser Spectroscopy

Background:

• Investigating nuclides far from the stability line is crucial for understanding nuclear properties.
• Laser spectroscopy provides sensitive probes of nuclear structure, including charge radii.
• Neutron-deficient isotopes offer unique insights into nuclear shell effects and forces.

Purpose of the Study:

• To determine the differential mean-square charge radii (δ⟨r²⟩) of neutron-deficient ^{52,53}Fe isotopes.
• To investigate the evolution of nuclear size across the N=28 neutron shell closure in iron isotopes.
• To provide experimental data for theoretical models of nuclear structure and density distributions.

Main Methods:

• Bunched-beam collinear laser spectroscopy was employed on ^{52,53}Fe, produced via in-flight separation and gas stopping.
• Isotope shifts of atomic hyperfine structures were measured to deduce δ⟨r²⟩ relative to stable ^{56}Fe.
• Multiconfiguration Dirac-Fock calculations were used to determine atomic factors for radius extraction.
• Nuclear density functional theory (with Fayans and Skyrme functionals) was used for theoretical interpretation.

Main Results:

• Differential mean-square charge radii were determined: δ⟨r²⟩^{56,52} = -0.034(13) fm² and δ⟨r²⟩^{56,53} = -0.218(13) fm².
• A minimum in δ⟨r²⟩ was observed at the N=28 neutron shell closure for the iron isotopic chain.
• The observed trend is attributed to the interplay of single-particle shell structure, pairing, and polarization effects.

Conclusions:

• The study successfully extended laser spectroscopy to neutron-deficient iron isotopes using a novel technique.
• The results provide critical experimental data on nuclear charge radii evolution around the N=28 shell closure.
• The findings contribute to a deeper understanding of nuclear forces and structure, comparable to trends in calcium isotopes.