Investigating the Pygmy Dipole Resonance Using β Decay

Area of Science:

• Nuclear Physics
• Nuclear Spectroscopy
• Exotic Nuclei

Background:

• The pygmy dipole resonance (PDR) is a key feature in nuclear structure, influencing reactions and properties of exotic nuclei.
• Understanding the PDR requires diverse experimental and theoretical approaches to probe its complex nature.
• Photon scattering and beta-decay spectroscopy are established techniques in nuclear structure studies.

Purpose of the Study:

• To investigate the potential of gamma-ray spectroscopy following beta decay as a probe for the pygmy dipole resonance.
• To compare the information obtained from beta-decay and photon scattering on the PDR.
• To elucidate the nature of nuclear states populated by beta decay within the PDR context.

Main Methods:

• Utilizing gamma-ray spectroscopy following beta decay of mother nuclei with low ground-state spin and high Q values.
• Comparing beta-decay data with existing photon scattering data, specifically ^{136}Xe(γ,γ^{'}) and ^{136}I β-decay to ^{136}Xe.
• Employing the quasiparticle phonon model (QPM) for theoretical calculations to interpret wave functions.

Main Results:

• Beta decay was found to populate 1⁻ levels associated with the pygmy dipole resonance.
• Only a fraction of the PDR states are populated through the studied beta decay.
• Beta decay predominantly populates complex configurations, which are weakly excited in inelastic scattering.

Conclusions:

• Gamma-ray spectroscopy following beta decay is a viable, complementary method for studying the pygmy dipole resonance.
• Beta decay offers unique insights into the complex wave function components of PDR states.
• The quasiparticle phonon model successfully describes the preferential population of complex configurations via beta decay.