SCALING PROPERTIES OF NUCLEI AWAY FROM STABILITY

Abstract

Atoms are the building blocks that constitute our world. At the core of an atom lies the nucleus which is composed of nucleons or protons and neutrons, essentially when looked at the MeV level or lower. These nucleons combine to form the elements and all the isotopes in the chart of the nuclides. Over the past few decades, lots of theoretical and experimental work have been done on nuclei lying away from limits of stability which are made up of short-lived, radioactive and loosely bound nuclei (called exotic nuclei). In this thesis, we focus our work to study the structure and properties of nuclei lying in the mediumamassaregion aroundaN = 20. Thisaregionais famed \island of inversion". The thesis consist of seven chapters and three appendices. In chapter 1, we present a brief introduction to the subject and the available experimental facilities for performing experiments with the beam of exotic nuclei. In chapter 2, we describes a short discussion of some of the theories used to describe breakup reactions leading to the post and prior forms of the transition matrix. In chapter 3, we present the mathematical formulations that goes in making of this thesis. We discuss two approaches namely, post form theory ofa niterangeadistorted waveaBorn approximation andaan analytical approach to draw physical insights in the breakup of exotic nuclei.In chapter 4, we computed theatotalalow-lying dipoleastrength for theamedium mass p-waveaone-neutronahalos 31Ne, 34Na and 37Mg using a simple analytic model. The comparison ofatheseaanalytic calculationsahas beenamade with thoseaperformed by the FRDWBA theory of Coulomb dissociation. We found a noticeable di erence between both of these estimates. Thus, we have proposed a new multiplicative correction factor to the analytical model, derived from a realistic Woods-Saxon potential, which helped us in re ning the model. Further, the comparison of both the theories shows reasonably good agreement, at least at the magnitude of the total dipole strengths level. Another important aspect apart from analyzing the peak of the dipole strength distribution is the comparison of the total dipole responses lead to a good estimate of the one-neutron separation energies for the p-wave halos. In Chapter 5, we investigate the behavior of electric dipole response functions of p-wave halos 29Ne, 31Ne, 34Na and 37Mg at nite deformations. In a further extension of the analytical model, we replace the bound state wave functions with deformed wave function and the continuum wave functions would still be spherical Bessel functions as in the case of neutron halos. This extension will be referred to as the semi-analytical (SA) model. We calculated the dipole response of 29Ne, 31Ne, 34Na and 37Mg corresponding to di erent deformation and con rmed that, within the SA approach, the dipole response is almost independent of the deformation e ects. We compare our semi-analytic estimates with the FRDWBA theory to see the e ects of quadrupole deformation on electric dipole responses of p-wave halos. The comparison of both theories shows a good agreement at some xed deformation values. In chapter 6, we investigate the theoretical breakup ofa29Ne on aa208Pb target at 244 MeV/u beam energy. As a part of the process, we calculate various reaction observables, like theaone-neutron removalacross-section,arelativeaenergy spectra, aangular andamomentumadistributions, etc. Comparing theacalculated crosssections with theaavailable experimentaladata, anae ort has also been made to put constraints on the large uncertainties in theaone-neutronaseparationaenergy of 29Ne. The summary and future prospect of the present work is discussed in chapter 7. Some mathematical details about the approximation used in this work is also given in appendix A.