The shell structure of nuclei was studied at PNPI by (p, 2p) and (p, np)
reactions using the 1 GeV proton beam of the PNPI syncrocyclotron . Both reactions were studied in identical kinematical conditions. The scattered proton was detected with a magnetic spectrometer, while the knocked out nucleon (p or n) was detected with a time-of-flight spectrometer. A number of nuclei (more than 20, from 6Li to 208Pb) were studied, and detailed information on the proton- and neutron-shell energies was obtained. Prior these measurements, the neutron shell energies were in most cases unknown. An important result of these studies was the observation of the 1s1/2 and 1p1/2 proton and neutron shells in heavy nuclei including 90Zr and 208Pb. The shell splitting was observed in many of the studied nuclei. This shell splitting was explained in terms of the spatial deformation of the self-consistent nuclear field. It has been shown that the data on the proton and neutron shell energies allow one to study the deformation parameters of the nuclear density distributions both for protons and neutrons. Also, the measured spectra show high sensitivity to the differences between the proton and neutron root-mean square radii. The obtained data can serve as a solid basis for testing the existing nuclear models and for developing new theoretical approaches to microscopic descriptions of the nuclear structure.
(For more detail review see article "Study of nuclear structure with quasielastic proton scattering at 1 GeV" in PNPI report of
the High Energy Physics Division "Main Scientific Activities 1971-1996").
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