Three-Body Model Calculation of Spin Distribution in Two-Nucleon Transfer Reaction

TL;DR

This study models two-nucleon transfer reactions using a three-body approach to analyze spin distributions, revealing their dependence on excitation energy and implications for the surrogate ratio method.

Contribution

It introduces a three-body model calculation for spin distributions in two-nucleon transfer reactions, highlighting the impact of excitation energy on the spin distribution shape.

Findings

Spin distribution shape is insensitive to incident energy and optical potentials.

The peak of the spin distribution shifts to higher spins with increasing excitation energy.

For the surrogate ratio method, excitation energy should be less than 10 MeV.

Abstract

The differential cross sections of two-nucleon transfer reactions 238U(18O,16O)240U around 10 MeV per nucleon are calculated by one-step Born-approximation with a 16O+2n+238U three-body model. The three-body wave function in the initial channel is obtained with the continuum-discretized coupled-channels method, and that in the final channel is evaluated with adiabatic approximation. The resulting cross sections have a peak around the grazing angle, and the spin distribution, i.e., the cross section at the peak as a function of the transferred spin, is investigated. The shape of the spin distribution is found not sensitive to the incident energies, optical potentials, and treatment of the breakup channels both in the initial and final states, while it depends on the excitation energy of the residual nucleus 240U. The peak of the spin distribution moves to the large-spin direction as the excitation energy increases. To fulfill the condition that the peak position should not exceeds 10 hbar, which is necessary for the surrogate ratio method to work, it is concluded that the excitation energy of 240U must be less than 10 MeV.