Narrow Results

We prove in this paper that the magnitude of anomaly in deuteron stripping reactions on A ≈ 80–110 mass target nuclei, at threshold of analogue channel, is proportional to the 3 - p wave neutron strength function. The result is obtained from analysis, within an empirical approach and computational frameworks, of the cross-section and analyzing power experimental data related to this (d,p) anomaly.

The p-wave threshold effect is described in terms of the reduced scattering matrix. The relationship of this approach to previous theoretical threshold models is established. We prove that this phenomenon is related to the reaction-mechanism of quasiresonant scattering: a single particle neutron threshold state and direct interaction coupling to open observed channels. Spectroscopic aspects of the threshold effect, both with respect to the magnitude and microstructure, are discussed in terms of the neutron strength function.

Three-body systems are studied in the framework of the Boundary Condition Model, in which the relevant interactions are expressed in terms of the scattering lengths of the two-body subsystems. We demonstrate explicitly the role of resonant states in the two-body subsystems and of multiple scattering between the constituents in producing a weakly bound three-body system, i.e. a Borromean nucleus. We obtain qualitative relations between the spatial extension of the three-body bound state, its energy, and the scattering lengths in the subsystems. The results are compared with experimental data for the Borromean nucleus ¹¹Li and ¹⁴Be.