Contribution of electric quadrupole and dipole-quadrupole interference terms in Coulomb breakup of 15 C
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NUCLEI Theory
Contribution of Electric Quadrupole and Dipole–Quadrupole Interference Terms in Coulomb Breakup of 15 C∗ P. Singh1)** , S. Kharb2), and M. Singh3) Received January 14, 2013
Abstract—The effects of electric quadrupole (E2) and dipole–quadrupole interference (E1–E2) terms in the Coulomb breakup of 15 C have been investigated within the framework of eikonal approximation. The sensitivity of Coulomb breakup cross section, differential in relative energy and Longitudinal Momentum Distribution (LMD) of core fragments, towards these terms have been examined. A very small (1% of E1) contribution of E2 transition has been predicted in integrated Coulomb breakup cross section. Further it is also found that the inclusion of E2 and E1–E2 terms introduces a small asymmetry in the peak of relative energy spectrum and also increases the peak height of the spectrum. The contribution of dipole– quadrupole interference terms is clearly shown in LMD, as it introduces an asymmetry in the shape of LMD and enhances the matching between the data and predictions. DOI: 10.1134/S1063778814010189
1. INTRODUCTION In CNO (Carbon–Nitrogen–Oxygen),
14 C(n, γ)
15 C(β − )15 N(n, γ)16 N(β − )16 O(n, γ)17 O(n, α)14 C
cycle the neutron capture reaction 14 C(n, γ)15 C attracts significant attention because of its considerable contribution in the synthesis of elements heavier than A > 20. Further, this reaction is also important in context of the ground-state configuration of 15 C, which is final state achieved by 14 C through neutron capture, as it has a moderate-sized neutron halo with low neutron binding energy [1–4]. Therefore, in order to predict the rate of reaction 14 C(n, γ)15 C the accurate information regarding the ground-state configuration of 15 C and the precise measurement of reaction cross section are required. Preferably, the reaction cross sections are to be directly measured in the laboratory. But, despite of many efforts, the required environment like high temperature and density cannot be attained for performing such experiments in the laboratory. However, in recent years several indirect methods like elastic scattering; Coulomb excitation and dissociation; transfer ∗
The text was submitted by the authors in English. Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal, Sonepat, India. 2) Department of Applied Sciences, JMIT, Radaur, India. 3) Department of Applied Sciences, TERII, Kurukshetra, India. ** E-mail: [email protected] 1)
reactions; nuclear knockout reactions; quasifree reactions; charge-exchange reactions, etc. have been developed to extract cross sections relevant to astrophysical processes [5]. The Coulomb dissociation process is being used frequently for obtaining the capture cross section in connection to astrophysical problems. But unfortunately it is not free from bias because of the presence of the contribution of electric quadrupole (E2) and dipole–quadrupole interference (E1–E2) terms [6, 7]. In order to obtain conclusive observations regarding the astrophys
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