In the realm of nuclear physics, understanding how nuclei respond to external fields is crucial for various applications, including energy production and nuclear waste management. Researchers like Futoshi Minato from the University of Tokyo are delving into these complexities to provide insights that could benefit the energy sector.
Minato’s recent study focuses on nuclear responses to two-body external fields, interpreted as double-phonon excitations, within the framework of the subtracted second random-phase approximation (SSRPA) for the oxygen-16 nucleus. The research aims to clarify the characteristics of these modes, which are essential for understanding nuclear behavior under various conditions.
The study begins by examining Hartree-Fock (HF) and SSRPA with the diagonal approximation. The resulting strength distributions are nearly identical, indicating that residual interactions in the one-particle-one-hole (1p-1h) sector contribute only weakly. This behavior contrasts with one-body excitations, where coupling between 1p-1h and two-particle-two-hole (2p-2h) configurations is crucial for generating collectivity.
In the full SSRPA calculation, which incorporates the residual interaction among 2p-2h configurations, the strength distributions are substantially modified. The double isoscalar (IS) 0+ and 2+ modes show pronounced redistribution, with peaks shifted to lower energies and additional strength emerging at higher energies. Conversely, the double isovector (IV) 1- mode shifts predominantly to higher energies due to a largely repulsive interaction.
Analysis of single transition amplitudes reveals that low-lying resonances are formed coherently through constructive neutron-neutron, proton-proton, and neutron-proton configurations. High-lying resonances, on the other hand, are dominated by neutron-proton configurations, reflecting their higher state density. These findings demonstrate that double-phonon excitations cannot be described by simple folding of one-body responses; a fully microscopic treatment of 2p-2h mixing, as provided by SSRPA, is essential.
For the energy sector, understanding these nuclear responses can have practical applications. For instance, in nuclear reactors, knowing how nuclei respond to external fields can help in designing more efficient and safer reactors. Additionally, in the field of nuclear waste management, understanding these responses can aid in developing better strategies for handling and disposing of nuclear waste.
The research was published in the journal Physical Review C, a reputable source for nuclear physics research. Minato’s work contributes to the broader understanding of nuclear behavior, which is vital for advancing nuclear energy technologies and ensuring their safe and efficient operation.
This article is based on research available at arXiv.