Reaction channel contributions to the triton + ²⁰⁸Pb optical potential

Keeley, N. and Mackintosh, R. S. (2023). Reaction channel contributions to the triton + ²⁰⁸Pb optical potential. Physical Review C, 107(3), article no. 034602.

DOI: https://doi.org/10.1103/PhysRevC.107.034602

Abstract

Background: Well-established coupled channel and coupled reaction channel (CRC) processes make contributions to elastic scattering that are not included in standard folding models of the optical model potential (OMP). Such contributions have been established for ³He interacting with ²⁰⁸Pb but the corresponding contributions for ³H are expected to be different, particularly for pickup coupling.

Purpose: To establish and characterize the contribution to the interaction potential between ³H and ²⁰⁸Pb that is generated by coupling to proton pickup (outgoing ⁴He) channels; also to study the contribution of collective states and identify effects of dynamical nonlocality due to these couplings.

Methods: CRC calculations, including coupling to collective states, will provide the elastic channel S- matrix S_lj resulting from the included processes. Inversion of S_lj will produce the local potential that yields, in a single channel calculation, the elastic scattering observables from the coupled channel calculation. Subtracting the bare potential from the inverted CRC potential yields a local and l- independent representation of the dynamical polarization potential (DPP). From the DPPs due to a range of combinations of channel couplings, the influence of dynamically generated nonlocality can be identified.

Results: Coupling to ⁴He channels makes a smaller contribution to the ³H interaction than it does for incident ³He. On the other hand coupling to inelastic channels makes a greater contribution than it does for ³He. The nonadditivity of the DPPs implies their dynamical nonlocality.

Conclusions: The DPPs established here challenge the notion that folding models, in particular local density models, provide a satisfactory description of elastic scattering of ³H from nuclei. Coupling to proton pickup channels induces dynamical nonlocality in the ³H OMP with implications for direct reactions involving ³H. Departures from a smooth radial form for the ³H OMP should be apparent in high quality fits to suitable elastic scattering data. Future theories of the interaction of ³H with nuclei should include some representation of outgoing ⁴He.

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