Structure of negative parity states at $${\mathbf {6}\,\lesssim \, \mathbf {E}_\mathbf {x} <{\mathbf {7.0}} }$$ 6
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Regular Article - Experimental Physics
< E < 7.0 MeV in 208 Pb Structure of negative parity states at 6 ∼ x A. Heusler1,a 1
Gustav-Kirchhoff-Str. 7/1, 69120 Heidelberg, Germany
Received: 22 November 2019 / Accepted: 18 April 2020 © The Author(s) 2020 Communicated by Robert Janssens
Abstract In the doubly magic nucleus 208 Pb states at ex< E < 7.0 MeV populated by the inelascitation energies 6 ∼ x tic proton scattering via the doublet isobaric analog resonances g7/2 +d3/2 in 209 Bi are studied. Sixteen states containing dominant strengths of the configurations g7/2 p3/2 , d3/2 p3/2 , g7/2 f5/2 , d3/2 f5/2 are newly assigned spins from 2− to 6− , among them ten states are newly identified. Amplitudes with relative signs of up to four one-particle one-hole configurations with strengths down to 0.05% are determined in 40 states with spins from 1− to 6− . Amplitudes of configurations d3/2 p1/2 , d3/2 p3/2 , d3/2 f5/2 for fourteen states and amplitudes of g7/2 p1/2 , g7/2 p3/2 , g7/2 f5/2 for twenty-seven states are determined. Total strengths up to the full strength are found for configurations d3/2 p1/2 , d3/2 p3/2 , d3/2 f5/2 with spins from 1− to 3− and for g7/2 p1/2 , g7/2 p3/2 , g7/2 f5/2 with spins from 1− to 6− .
1 Introduction The heaviest doubly magic nucleus 208 Pb is fascinating as it offers the opportunity to study different classes of nuclear excitations. Most states in 208 Pb are described in the shell model (SM) by one-particle one-hole (1p1h) configurations. More than two dozen states below the neutron and proton threshold (S(n) = 7368 keV, S( p) = 8004 keV [1]) are recognized to be not described as 1p1h configurations. At E x ≈ 6.0 MeV configurations built by the coupling of the 3− yrast state with 1p1h configurations were identified in eighteen states [2]. Ten states at 2 < E x < 8 MeV were recognized as tetrahedral configurations [3,4]. Four states at E x < 5.9 MeV are pairing vibrations [5–7]. Four states at E x < 6.2 MeV are suggested to be icosahedral configurations [8].
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Negative parity states below E x = 7.0 MeV are almost completely identified by this work. It allows to find positive parity states and non-1p1h states [9] by comparison to SM calculations [10–13]. The surface delta interaction (SDI) was introduced by Green and Moszkowski [14] and extensively discussed by Talmi [15]. It provides a simple method to understand the interaction among two particles in a complex nucleus [2,15– 18]. The essential tool to determine amplitudes of 1p1h configurations in states of 208 Pb derives from the study of isobaric analog resonances (IAR) [19–53]. It allows to obtain information about the residual interaction among one-particle one-hole configurations [31–34]. IARs in 209 Bi strongly excite only negative parity states. Early data were obtained in 1965–1970 in the USA [21– 30] and in 1968–1969 at Heidelberg (Germany) [35–42]. In 2003–2019 more data were obtained at the Maier-LeibnitzLaboratorium (MLL) at Garching (Ger
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