Probing Near-Threshold $s$-Wave Components in Heavy Nuclei via Coulomb-Assisted Neutron Transfer

TL;DR

This paper introduces a Coulomb-assisted neutron transfer method at low energies to probe weakly bound s-wave neutron components near the neutron emission threshold in heavy nuclei.

Contribution

It presents a novel approach using low-energy $(d,p)$ reactions to selectively access the asymptotic s-wave neutron wave functions in heavy nuclei.

Findings

Cross sections for weakly bound states are weakly dependent on incident energy.

Strongly bound states' cross sections decrease rapidly with decreasing energy.

The method enhances sensitivity to s-wave components due to centrifugal barrier suppression of higher l orbitals.

Abstract

We propose a method to probe weakly bound s-wave neutron components near the neutron emission threshold in heavy nuclei using Coulomb-assisted neutron transfer reactions. Weakly bound s-wave neutrons have large asymptotic amplitudes, which are difficult to access directly with conventional methods. This work focuses on the $(d,p)$ reaction at low incident energies and backward angles, where the reaction is localized in the nuclear exterior due to the Coulomb barrier. Under these conditions, the transition amplitude becomes sensitive to the asymptotic part of the single-particle wave function. Finite-range DWBA calculations show that the cross section for weakly bound states exhibits a weak dependence on incident energy, while that for strongly bound states decreases rapidly with decreasing energy. Contributions from orbitals with $l \geq 1$ are suppressed by the centrifugal barrier, resulting in selectivity for s-wave components. This method provides a probe of the strength distribution of weakly bound s-wave components near threshold and the asymptotic structure of their wave functions.