Deformation and Collectivity in Doubly Magic ^{208}Pb

Area of Science:

• Nuclear Physics
• Atomic Physics

Background:

• Lead-208 (Pb-208) is the heaviest known doubly magic nucleus.
• Despite its magicity, Pb-208 exhibits strong octupole correlations and quadrupole collectivity.

Purpose of the Study:

• To investigate the nuclear structure of Lead-208.
• To precisely measure the spectroscopic quadrupole moments of specific excited states.

Main Methods:

• Utilized four Coulomb-excitation measurements.
• Employed state-of-the-art experimental equipment.

Main Results:

• Conclusively demonstrated a large, negative spectroscopic quadrupole moment for the 3- (octupole) and 2+ (quadrupole) states.
• Indicated a preference for prolate deformation in these states.
• Observed quadrupole moment is discussed in relation to two-phonon states and coupled motion.

Conclusions:

• Current theoretical models fail to reproduce the sign and magnitude of the observed deformation in Pb-208.
• Lead-208 continues to present a puzzle for nuclear structure understanding.