Background of Existence of the Two Low-Lying Adjacent 4⁺ Narrow Resonances in ¹⁶O Nucleus and Other 4-Boson Systems

Based on an analysis of the inherent nodal structures of wave functions of 4-boson systems, we found that the internal energy of the 4⁺₁ state should be lower because its structure can be optimized without suffering a strong constraint arising from symmetry (while other 1≤L≤3 states suffer from this kind of constraints). Furthermore, two superior structures favorable in binding are found to be allowed to be possessed by 4⁺ states. These findings would lead to the appearance of two adjacent 4⁺ states, as a common feature, in the low-lying spectra of 4 boson systems.