ΔI=2 Bifurcation as a Characteristic Feature of Scissors Rotational Bands

Area of Science:

• Nuclear Physics
• Quantum Mechanics
• Condensed Matter Physics

Background:

• Nuclear scissors vibrations are collective modes involving the relative motion of proton and neutron bodies.
• Rotational bands in deformed nuclei are characterized by sequences of energy levels with increasing spin.
• Previous studies have not fully explained the observed splitting in rotational bands associated with scissors vibrations.

Purpose of the Study:

• To investigate the microscopic origin of the observed splitting (ΔI=2 bifurcation) in rotational bands based on nuclear scissors vibrations.
• To elucidate the role of self-organization and specific nuclear configurations in this phenomenon.
• To provide a theoretical explanation for puzzling experimental observations in nuclei like $^{156}$Gd.

Main Methods:

• Microscopic many-body calculations were employed to model the nuclear structure and dynamics.
• The calculations focused on the behavior of the moment of inertia in relation to spin states.
• Analysis included the influence of K^{π}=1^{+} two-quasiparticle configurations.

Main Results:

• Rotational bands exhibit systematic splitting between neighboring spin states (ΔI=2 bifurcation).
• The magnitude of the moment of inertia oscillates between even and odd spin states.
• This bifurcation is attributed to the self-organization of proton and neutron bodies during scissors motion, amplified by specific configurations.

Conclusions:

• The study provides a theoretical framework for understanding the bifurcation in nuclear scissors vibrations.
• The findings explain the puzzling excited state in $^{156}$Gd as the first evidence of this effect.
• Bifurcation is predicted to be a general feature in deformed nuclei and potentially other systems with collective scissors vibrations.