Novel ΔJ=1 Sequence in ^{78}Ge: Possible Evidence for Triaxiality.

Area of Science:

• Nuclear Physics
• Atomic Physics

Background:

• Low-energy nuclear structure studies are crucial for understanding nuclear forces.
• Germanium (Ge) and Selenium (Se) isotopes provide insights into nuclear shell effects and collective excitations.

Purpose of the Study:

• To investigate the low-energy level structure and decay properties of the ⁷⁸Ge nucleus.
• To compare experimental findings with theoretical predictions from shell-model and rotor models.

Main Methods:

• Experimental identification of excited states in ⁷⁸Ge using nuclear spectroscopy techniques.
• Theoretical calculations employing the nuclear shell model.
• Application of the Davydov-Filippov-Rostovsky model for rigid-triaxial rotors.

Main Results:

• A sequence of levels (2⁺ to 6⁺) in ⁷⁸Ge was identified with unique ΔJ=1 decay transitions, differing from neighboring nuclei.
• Shell-model calculations accurately predicted energies and branching ratios but failed to reproduce observed transition probabilities.
• Rotor model calculations showed qualitative agreement with decay patterns but predicted incorrect excitation energies.

Conclusions:

• The observed decay pattern in ⁷⁸Ge presents a puzzle for existing nuclear structure theories.
• The findings suggest limitations in current models for describing collective phenomena in this mass region.
• Further theoretical and experimental investigations are needed to fully understand the structure of ⁷⁸Ge.