Illustration of a nuclear reaction with proton, deuteron, and gamma rays against a starfield background.

Unlocking Nuclear Secrets: How (p,d) Reactions Could Revolutionize Nuclear Physics

Author's portrait.
Theo Raines in Science & Nature August 2025 • 4 min read.

"New research explores using (p,d) reactions to refine our understanding of neutron capture, potentially impacting astrophysics and nuclear technology."


Neutron-capture reactions, where a neutron is absorbed by an atomic nucleus, are fundamental processes in the cosmos. They play a crucial role in the creation of heavy elements in stars and are also important in nuclear technology. However, studying these reactions, particularly with unstable isotopes (atoms with an imbalance of neutrons and protons), presents significant challenges.

Directly measuring neutron capture on unstable isotopes is often impossible due to their short lifespans and the difficulty in producing them in sufficient quantities. As a result, scientists rely on theoretical calculations to predict the likelihood of these reactions. But these calculations are only as good as the information that goes into them, and uncertainties in nuclear properties can lead to significant errors in the predictions.

To overcome these limitations, researchers are developing indirect methods to constrain these calculations. One promising technique involves studying (p,d) reactions – nuclear reactions where a proton collides with a nucleus, resulting in a deuteron (a nucleus consisting of one proton and one neutron) being emitted. By carefully analyzing these reactions, scientists hope to gain insights into the properties of the compound nucleus formed, and ultimately, to refine our understanding of neutron capture.

Deciphering Nuclear Reactions: The Power of (p,d) Reactions

Illustration of a nuclear reaction with proton, deuteron, and gamma rays against a starfield background.

The heart of this research lies in the statistical Hauser-Feshbach formalism, a theoretical framework used to describe nuclear reactions. This formalism accounts for the conservation of fundamental quantities like angular momentum and parity (a property related to the symmetry of a nucleus). In essence, it allows scientists to break down a complex nuclear reaction into a series of simpler steps, each with its own probability.

The challenge, however, lies in accurately determining these probabilities. They depend on factors such as the transmission coefficients (which describe the likelihood of particles entering or leaving the nucleus) and the level densities (which describe the number of available energy states in the nucleus). These quantities are often poorly known, especially for unstable isotopes.

To improve the accuracy of these calculations, scientists are turning to (p,d) reactions. Here’s how this method works:
  • Creating the Compound Nucleus: A proton (p) interacts with a target nucleus, resulting in the formation of a compound nucleus – the same nucleus that would be formed in a neutron capture reaction.
  • Analyzing the Decay: The compound nucleus then decays, emitting particles such as neutrons or photons (gamma rays). By measuring the properties of these emitted particles, scientists can gather information about the structure and properties of the compound nucleus.
  • Constraining the Calculations: The data obtained from the (p,d) reaction is then used to refine the parameters in the Hauser-Feshbach calculations, reducing the uncertainties in the predicted neutron capture cross sections.
One of the key advantages of this approach is that (p,d) reactions can be performed on a wider range of isotopes than direct neutron capture measurements. This opens up the possibility of studying neutron capture on unstable isotopes that are crucial for understanding the synthesis of heavy elements in stars.

The Future of Nuclear Physics: More Precise Models and Exotic Isotopes

By combining experimental data from (p,d) reactions with advanced theoretical models, scientists are paving the way for a more complete and accurate understanding of nuclear processes. This knowledge will not only help us unravel the mysteries of the universe but also has practical applications in nuclear technology, medicine, and energy.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1051/epjconf/201714612014, Alternate LINK

Title: Capture Cross Sections From (P,D) Reactions

Subject: General Medicine

Journal: EPJ Web of Conferences

Publisher: EDP Sciences

Authors: J.E. Escher, J.T. Burke, R.J. Casperson, R.O. Hughes, S. Ota, N.D. Scielzo

Published: 2017-01-01

Everything You Need To Know

1

What exactly is a (p,d) reaction and why is it relevant?

A (p,d) reaction is a nuclear reaction where a proton collides with a nucleus, resulting in the emission of a deuteron. This method is employed to gain insights into neutron capture, a process crucial in astrophysics for understanding how heavy elements are created in stars. By analyzing the (p,d) reactions, scientists can gather data about the compound nucleus, helping to refine calculations related to neutron capture.

2

Why is neutron capture an important process?

Neutron capture is a fundamental process where an atomic nucleus absorbs a neutron. This process is important because it's how heavy elements are created in stars and it's also significant in nuclear technology. Studying neutron capture, especially with unstable isotopes, is challenging. This makes indirect methods like (p,d) reactions very important to improve our understanding of the process.

3

What is the Hauser-Feshbach formalism, and how does it relate to this research?

The Hauser-Feshbach formalism is a theoretical framework used to describe nuclear reactions. It helps scientists understand complex reactions by breaking them down into simpler steps, considering factors like angular momentum and parity. However, the accuracy of these calculations depends on knowing probabilities and parameters such as transmission coefficients and level densities. Using (p,d) reactions allows for more accurate determination of these probabilities, thus improving the accuracy of Hauser-Feshbach calculations.

4

How are (p,d) reactions used to study neutron capture?

Scientists use (p,d) reactions to refine calculations related to neutron capture by first creating a compound nucleus when a proton interacts with a target nucleus. Then, they analyze the decay of this compound nucleus, measuring the properties of emitted particles like neutrons or gamma rays. This data is then used to refine the parameters within the Hauser-Feshbach calculations. This process reduces the uncertainties in predicting neutron capture cross sections, which is essential for understanding nuclear processes.

5

What are the broader implications of this research?

The significance of this research lies in its ability to improve our understanding of neutron capture, especially for unstable isotopes that are hard to study directly. This has implications for astrophysics by improving models of how elements are created in stars. Furthermore, this research has practical applications in nuclear technology, medicine, and energy, ultimately leading to more precise models for nuclear processes.

Newsletter Subscribe

Subscribe to get the latest articles and insights directly in your inbox.