Comparison of halo of 11 Be, 15 C, and 19 C
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NUCLEI Theory
Comparison of Halo of
11
Be,
15
C, and
19
C*
R. Kharab** , R. Kumar, P. Singh, and H. C. Sharma1) Department of Physics, Kurukshetra University, India Received November 24, 2006; in final form, February 28, 2007
Abstract—We have compared the halo of 11 Be,15 C, and 19 C nuclei by analyzing the one-neutron stripping reaction data on the Be target at 60-, 54-, and 57-MeV/A beam energies, respectively, within the framework of the eikonal approximation approach. The determination of effective range through the comparison of the total cross section data and prediction has revealed that the halo of 19 C is the well developed, while that of 15 C is the least and that of 11 Be lies in between these two. The longitudinal momentum distribution data also strengthen these observations. PACS numbers: 25.60.Gc, 25.70.Mn, 25.60.Dz DOI: 10.1134/S1063778807120095
1. INTRODUCTION Following the pioneering work of Tanihata et al. [1], the breakup reactions of unstable nuclei lying in the close vicinity of the neutron/proton drip line have confirmed the existence of a novel nuclear structure frequently refered to as nucleon halo. This peculiar nuclear structure consists of a nuclear core with normal nuclear density and one or two diffused valence nucleon(s). This threshold effect may be attributed to the tunneling out of the outermost valence nucleon(s) to the classically forbidden region. An unexpectedly large matter radius, long tail in density distribution, small binding energy, and narrow longitudinal momentum distribution (LMD) of the constituent fragments in their ground state are some of the characteristic features of the halo nuclei. Because of these unique ground-state properties of halo nuclei, their breakup cross section on a light or heavy target has been found to be significantly enhanced. In case of light target and at small impact parameter, the breakup occurs predominantly by the nuclear interaction between the participants through two different mechanisms, namely, stripping and diffraction dissociation. In the stripping reaction, one of the constituent fragments of the projectile is absorbed by the target, while the other goes out [2]. The stripping reaction involving halo nuclei represents an efficient tool to ascertain various ground-state properties of ∗
The text was submitted by the authors in English. Department of Applied Sciences, Haryana College of Technology and Management, Kaithal, India. ** E-mail: [email protected] 1)
these nuclei [3]. So far, a number of different theoretical models have been proposed to deal with the stripping reactions of halo nuclei [2, 4–7]. However, at high energies, the eikonal approximation approach has been considered the most convenient [8]. Experimentally, one-neutron (11 Be, 19 C) [9, 10], one-proton (8 B) [11], and two-neutron (11 Li) [12] halo structures have been well established. However, the nuclei with one valence neutron occupying the l = 0 orbital have attracted significant attention. Besides being simple, the absence of centrifugal and Coulomb bar
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