Weak Binding Effects in Nuclear Structure: 40Mg and The Kerman Problem in the Continuum

Thursday 6 June 2019, 2.00PM

Speaker(s): Augusto Macchiavelli, Lawrence Berkeley National Laboratory, USA


The effect of weak binding on nuclear structure, decay, and reactions is an open question in nuclear physics. On the neutron-rich side of stability, as the neutron separation energy approaches zero, weakly bound neutrons in the single-particle levels at the Fermi surface approach the edge of the nuclear potential and may move outside the core of well-bound nucleons, and possibly couple to unbound continuum states. The nature of this transition from a “closed” to an “open” quantum system [1], where binding is dominated by correlations rather than the mean field, has only just begun to be explored, and our understanding of weak-binding effects and coupling to the continuum is, in many ways, nascent.

The first spectroscopic study of the near drip-line Nucleus 40Mg, revealed two γ-ray transitions that suggest an excitation spectrum with unexpected properties as compared to both the systematics along the lighter Mg isotopes and available state-of-the-art theoretical model predictions. We will discuss a possible explanation for the observed structure in terms of weak-binding effects.

In 1956 Kerman published a seminal paper on rotational perturbations in nuclei [3]. In the second part of the talk, we consider Kerman’s problem when one of the single-particle levels involved is a resonant state. We will present some preliminary results showing the behavior of the moment of inertia and the decoupling parameter as a function of the state width.

[1] J. Dobaczewski, et al. Prog. Part. Nucl. Phys. 59, 432 (2007).
[2] H. L. Crawford, et al. Phys, Rev. Lett. 122, 052501 (2019).
[3] A. Kerman, Mat. Fys. Medd. Dan. Vid. Selsk., no. 15 (1956).

*This material is based upon work supported by the U.S. DOE, Office of Science, Office of Nuclear Physics, under Contract No. DEAC0205CH11231.

Location: P/L/002