Experimental studies of the nuclear spatial structure of neutron-rich He and Li isotopes
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Experimental Studies of the Nuclear Spatial Structure of Neutron-Rich He and Li Isotopes* G. D. Alkhazov** , A. V. Dobrovolsky, and A. A. Lobodenko Petersburg Nuclear Physics Institute, Russian Academy of Sciences, Gatchina, 188350 Russia Received October 3, 2005
Abstract—Results of several experiments aimed at exploring the nuclear spatial structure of neutron-rich He and Li isotopes are presented and briefly discussed. The study of the density distributions in these nuclei by small-angle proton elastic scattering at intermediate energy is considered in more detail. The performed investigations allow one to obtain information on the total matter distributions, radii of the matter, neutron and proton distributions, effective and internal core sizes, halo sizes, and spatial correlations of the halo nucleons in the studied nuclei. PACS numbers : 27.20.+n, 21.10.Gv, 21.10.Ft, 25.40.Cm, 24.10.Ht, 25.60.Dz DOI: 10.1134/S1063778806070052
1. INTRODUCTION Since the discovery of halo nuclei by Tanihata et al. [1], a great number of experiments of different types have been carried out to investigate the spatial structure of these nuclei. In particular, in order to study the nuclear structure of neutron-rich He and Li isotopes, the nucleus–nucleus interaction cross sections and cross sections for removal of a few neutrons were measured, the momentum distributions of the nuclear fragments and neutrons emerging in the nuclear breakup and Coulomb dissociation reactions were studied, several laser spectroscopy experiments were performed, and the nucleus–nucleus and proton–nucleus elastic scattering was investigated. Owing to these investigations, valuable information on the spatial structure of the 6,8 He and 8,9,11 Li nuclei has been obtained. Some of the experimental results for 6,8 He and 8,9,11 Li are presented in the paper, and it is demonstrated that a combination of the results obtained by different methods provides detailed information on the spatial structure of these nuclei. 2. INTERACTION CROSS SECTIONS The total interaction (reaction) nucleus–nucleus cross sections [1] were used for determining the size of halo nuclei. Note that the interaction cross sections may be measured with sufficiently high accuracy. Unfortunately, deducing the nuclear matter radii from the measured cross sections meets with some difficulties. ∗ **
The text was submitted by the authors in English. E-mail: [email protected]
In experiment, one usually measures with the transmission method the so-called total interaction cross section σi , while theory allows one to calculate with high accuracy the total reaction cross section σr . When extracting the value of the nuclear matter radius from the measured interaction cross section σi , a small difference between σi and σr , as well as a contribution to the cross section from the Coulomb interaction, may be taken into account. It should be admitted, however, that the account of these effects involves some uncertainties. For calculations of the reaction cross sections, one can use the multiplesca
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