Neutron drip line in odd and even mass calcium and nickel nuclei

Abstract

Neutron rich Ca and Ni nuclei have been studied in spherical Relativistic Mean Field formalism in co-ordinate space. A delta interaction has been has been adopted to treat the pairing correlations for the neutrons. Odd nuclei have been treated in the blocking approximation. The effect of the positive energy continuum and the role of pairing in the stability of nuclei have been investigated using the resonant-BCS (rBCS) approach. In Ca isotopes, N = 50 is no longer a magic number while in Ni nuclei, a new magic number emerges at N = 70. There is a remarkable difference in the relative positions of the drip lines for odd and even isotopes. In Ca isotopes, the last bound even and odd nuclei are found to be 72 Ca and 59 Ca, respectively. In Ni isotopes, the corresponding nuclei are 98 Ni and 97 Ni, respectively. The origin of this difference in relative positions of the dripline in even and odd isotopes in the two chain is traced to the difference in the single particle level structures and consequent modification in the magic numbers in the two elements. Pairing interaction is seen to play a major role. The effect of the width of the resonance states on pairing has also been investigated.PACS numbers: 21.60. Jz,27.40.+z,27.50.+e,27.60.+j In recent years, it has been possible to populate and study a number of neutron rich nuclei from fusion evaporation reactions using radioactive ion beams as well as from fission fragment studies. The last bound neutrons in such a nucleus may lie very close to the continuum and the effect of the positive energy continuum on the structure of such nuclei should be studied carefully. Another very important aspect of nuclei near the drip line is the additional stability provided by the pairing interaction. It is important to study the effect of pairing by studying the odd mass nuclei along with the even mass ones. Although a number of such studies has been undertaken in lighter mass regions, nuclei in the medium and the heavy mass regions have not yet been studied in sufficient detail. In the present calculation, neutron rich Ca and Ni nuclei have been studied using the Relativistic Mean Field (RMF) formalism in co-ordinate space.RMF theory is a major tool of nuclear structure physics. Very often, the RMF equations are solved by expanding in a harmonic oscillator basis. However, it is well known that the basis expansion approach using the harmonic oscillator basis cannot explain the density in halo nuclei near the drip line because of slow convergence in the asymptotic region. Nonrelativistic Hartree Fock Bogoliubov (HFB) and Relativistic Hartree Bogoliubov (RHB) methods in co-ordinate space have emerged as two very accurate approaches of treating the nuclei very close to the drip line.The effect of the states in the continuum has been incorporated in most of the calculations by solving the equations in coordinate space using the box normalization condition, thus replacing the continuum with a set of discrete positive energy states. However, in this case, the single particle energy l...

Characterization of fragment emission inNe20(7–10 MeV/nucleon)+C12Dey1, Bhattacharya2, Bhattacharya3 et al. 2007Phys. Rev. C19020View full textAdd to dashboardCite

“…With this motivation, we have studied the fragment emission spectra from the reaction 20 Ne + 12 C at E lab = 145, 158, 170, 180 and 200 MeV, respectively. A part of the present data has already been reported [4], which showed enhancement in yield of Carbon and Boron fragments well above the standard statistical model predictions.…”

“…Several experiments have been done in recent years to understand the mechanism of complex fragment emission in low-energy (E lab < ∼ 10 MeV/nucleon) light heavy-ion (A projectile + A target < ∼ 60) reactions [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. The origin of these fragments extends from quasi-elastic (QE)/ projectile breakup [2,3], deep-inelastic (DI) transfer and orbiting [4,6,12,13,14,15,16], to fusion-fission (FF) [18,19,20,21,22,23] processes; and in some cases the structure of the nuclei has been found to play an important role.…”

“…The origin of these fragments extends from quasi-elastic (QE)/ projectile breakup [2,3], deep-inelastic (DI) transfer and orbiting [4,6,12,13,14,15,16], to fusion-fission (FF) [18,19,20,21,22,23] processes; and in some cases the structure of the nuclei has been found to play an important role. In most of the reactions studied, the observed fully energy-damped yields of the fragments have been successfully explained in terms of fusion-fission (FF) mechanism [18,19,20,21,22,23].…”

Elastic magnetic form factors of exotic nuclei

“…49 Ca is another nucleus with a single neutron outside the doubly closed core. 59 Ca is found to be the odd-A neutron drip-line of Ca isotopes in the RMF theory [50]. The densities of the last neutron of 49 that the shape of the densities are similar as expected, since the shape of the density is mainly determined by the node number and the orbital angular momentum (or centrifugal potential).…”

A shell-model study of calcium isotopes towards their drip line

“…In this context, calcium isotopes are one of the most intriguing subjects to be investigated, since this isotopic chain spans from the neutron-deficient 36 Ca, which lies close to the proton drip line, up to 60 Ca, that has been recently observed [2] and whose N/Z ratio, equal to 2, classifies it as a very exotic nuclear system. As a matter of fact, the observation of 60 Ca draws a line between studies predicting it as a loosely bound nucleus [3][4][5] and those pushing neutron drip line up to 70 Ca [6][7][8][9]. Moreover, recent mass measurements of heavy calcium isotopes [10,11] are helpful to narrow the spread of the theoretical predictions about this yet undiscovered section of the chart of nuclides.…”