Core excitations across the neutron shell gap in 207Tl

Wilson, E.; Podolyák, Zs.; Grawe, H.; Brown, B. A.; Chiara, C. J.; Zhu, S.; Fornal, B.; Janssens, R. V. F.; Shand, C. M.; Bowry, M.; Bunce, M.; Carpenter, M. P.; Cieplicka-Oryńczak, N.; Deo, A. Y.; Dracoulis, G. D.; Hoffman, C. R.; Kempley, R. S.; Kondev, F. G.; Lane, G. J.; Lauritsen, T.; Lotay, G.; Reed, M. W.; Regan, P. H.; Rodríguez Triguero, C.; Seweryniak, D.; Szpak, B.; Walker, P. M.

doi:10.1016/j.physletb.2015.04.055

Title: Core excitations across the neutron shell gap in 207Tl

Journal Article · Wed Jul 01 00:00:00 EDT 2015 · Physics Letters B

DOI:https://doi.org/10.1016/j.physletb.2015.04.055· OSTI ID:1198546

Wilson, E.; Podolyák, Zs.; Grawe, H.; Brown, B. A.; Chiara, C. J.; Zhu, S.; Fornal, B.; Janssens, R. V. F.; Shand, C. M.; Bowry, M.; Bunce, M.; Carpenter, M. P.; Cieplicka-Oryńczak, N.; Deo, A. Y.; Dracoulis, G. D.; Hoffman, C. R.; Kempley, R. S.; Kondev, F. G.; Lane, G. J.; Lauritsen, T. more »

The single closed-neutron-shell, one proton–hole nucleus ²⁰⁷Tl was populated in deep-inelastic collisions of a ²⁰⁸Pb beam with a ²⁰⁸Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N=126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations using two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states.

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