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.



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 Slj resulting from the included processes. Inversion of Slj 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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