Elsevier

Nuclear Physics A

Volume 462, Issue 2, 26 January 1987, Pages 221-251
Nuclear Physics A

Proton hole response function on 196Pt and 197Au transitional target nuclei up to high excitation energy

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Abstract

The proton-hole response functions have been studied on the transitional target nuclei 196Pt and 197Au via the (d, 3 He) reaction at Ed = 108.4 MeV, up to 6 MeV and 18.5 MeV excitation energy respectively. 196Pt low-lying levels have been studied in addition at Ed = 50 MeV.

Spectroscopic information gained on the low-lying levels in the 195Ir and 196Pt residual nuclei allows the discussion of the 3s12 and 2d32 orbital filling. For both 195Ir and 196Pt, new 2d52 and 1h112 levels or groups are observed.

The 196Pt spectra exhibit a broad bump between 6 and 15 MeV excitation energy riding over a continuous background. The study of the excitation energy spectra up to 27 MeV leads to a consistent subtraction of the background. The contributions of the 1g92, 2p and 1f inner-hole strengths are deduced by least square fits of DWBA angular distributions. About the whole 1g92 and 2p inner hole strengths and 50% of the 1f strengths are found below Ex = 18.5 MeV. The background correction is also used to reanalyse previous data obtained via the same reaction on the spherical 208Pb target for comparison.

Experimental results on centroid separation energies are compared with Hartree Fock predictions. The spreading widths and specific features of the strength distribution shapes in 195Ir and 196Pt and 207Tl are discussed in connection with the dominant quadrupole collective degrees of freedom of the two first nuclei contrasting with the strong vibrational modes in 207Tl. The valence hole fragmentation in 195Ir is described in the framework of the core quasiparticle coupling model.

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    Present address: Istituto di Fisica, Universita di Milano, Italy.

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