Important Influence of Entrance Channel Reorientation Coupling on Proton Stripping
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Letter to the Editor
Important Influence of Entrance Channel Reorientation Coupling on Proton Stripping N. Keeley1,a , K. W. Kemper2,3 , K. Rusek3 1
National Centre for Nuclear Research, ul. Andrzeja Sołtana 7, 05-400 Otwock, Poland Department of Physics, Florida State University, Tallahassee, Florida 32306, USA 3 Heavy Ion Laboratory, University of Warsaw, ul. Pasteura 5a, 02-093 Warsaw, Poland
2
Received: 19 August 2020 / Accepted: 2 October 2020 © The Author(s) 2020 Communicated by Nicolas Alamanos
Abstract While it is well established that the ground state reorientation coupling can have a significant influence on the elastic scattering of deformed nuclei, the effect of such couplings on transfer channels has been much less well investigated. In this letter we demonstrate that the 208 Pb(7 Li,6 He)209 Bi proton stripping reaction at an incident energy of 52 MeV can be well described by the inclusion of the 7 Li ground state reorientation coupling within the coupled channels Born approximation formalism. Full finite-range distorted wave Born approximation calculations were previously found to be unable to describe these data. Addition of coupling to the 0.478-MeV 1/2− excited state of 7 Li, together with the associated two-step transfer path, has little or no influence on the shape of the angular distributions (except that for stripping leading to the 1.61-MeV 13/2+ level of 209 Bi which is significantly improved) but does affect appreciably the values of the 209 Bi → 208 Pb + p spectroscopic factors. Implications for experiments with weaklybound light radioactive beams are discussed. While the distorted wave Born approximation in its full finiterange version (FR-DWBA) has been applied to the analysis of a wide body of heavy-ion reaction data with considerable success, it has been known since the early 1970s that certain classes of reaction, in particular (but by no means restricted to) single-proton transfers, cannot be satisfactorily described using it without recourse to such undesirable expedients as ad hoc adjustments of the exit channel optical potential parameters. These adjustments are usually such that the resulting parameters no longer describe the relevant elastic scattering, thus violating one of the fundamental tenets of the DWBA. Many of these reactions are poorly matched, either in terms of Q value or transferred angular momentum, and at the time this led to the conjecture that the inclusion of two-step reaca e-mail:
[email protected] (corresponding author)
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tion paths via excited states of the projectile and/or ejectile within the coupled channels Born approximation (CCBA) formalism would enable good descriptions to be obtained without the need arbitrarily to modify the exit channel distorting potentials. However, the prohibitive computational overhead of such calculations with then available resources precluded the testing of this hypothesis. There the question has remained in many cases for the intervening four decades as interest in heavy-ion reactions wa
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