# Structure and decay at rapid proton capture waiting points

## TL;DR

This paper models proton capture and dissociation processes near A≈70 using a three-body approach, revealing resonance structures that influence astrophysical reaction rates and proposing a simple formula for low-temperature rates.

## Contribution

It introduces a three-body framework to compute reaction rates for proton capture near A≈70, highlighting resonance effects and providing a simple low-temperature rate formula.

## Key findings

- Resonance peaks in photon dissociation cross section at low energies.
- Reaction rates depend on temperature and nuclear resonance structures.
- A simple formula accurately reproduces complex reaction rate calculations at low temperatures.

## Abstract

We investigate the region of the nuclear chart around $A \simeq 70$ from a three-body perspective, where we compute reaction rates for the radiative capture of two protons. One key quantity is here the photon dissociation cross section for the inverse process where two protons are liberated from the borromean nucleus by photon bombardment. We find a number of peaks at low photon energy in this cross section where each peak is located at the energy corresponding to population of a three-body resonance. Thus, for these energies the decay or capture processes proceed through these resonances. However, the next step in the dissociation process still has the option of following several paths, that is either sequential decay by emission of one proton at a time with an intermediate two-body resonance as stepping stone, or direct decay into the continuum of both protons simultaneously. The astrophysical reaction rate is obtained by folding of the cross section as function of energy with the occupation probability for a Maxwell-Boltzmann temperature distribution. The reaction rate is then a function of temperature, and of course depending on the underlying three-body bound state and resonance structures. We show that a very simple formula at low temperature reproduces the elaborate numerically computed reaction rate.