News - Origin of Lead

Origin of Lead

A. Casanovas, one of our team members, recently published paper: "Shedding light on the origin of 204Pb, the heaviest s-process–only isotope in the solar system" (Physical review letters, 10.1103/PhysRevLett.133.052702), has been highlighted at CERN's EP Newsletter.

Background

Lead is common: It's found throughout our solar system and especially on Earth.

Lead has four main types: These are the isotopes: 204Pb, 206Pb, 207Pb, and 208Pb.
Most lead comes from radioactive decay: Three types of lead (206Pb, 207Pb, and 208Pb) are created when uranium and thorium break down over time.
One type of lead is special: 204Pb is unique because it's not created from radioactive decay.
204Pb is a clue to how stars make elements: Scientists believe almost all 204Pb was made inside stars during a phase called the "AGB stage."
Studying 204Pb helps us understand how stars work: By comparing how much 204Pb we find in meteorites with what models predict, we can test our understanding of how stars create heavy elements.
Accurate measurements are key: To get precise results, we need to know how easily 204Pb captures neutrons. This is called the "neutron capture cross-section."
Experiments are crucial: While models can give estimates, experiments are the best way to determine the neutron capture cross-section.
A missing piece of the puzzle: Until recently, accurate measurements were difficult because we lacked information about the element that turns into 204Pb, which is 204Tl.

In simpler terms,

Imagine you're building a model car. You have instructions, but some parts are missing. 204Pb is like a special part that helps us understand how the entire car (the star) was built. To understand how that part fits, we need precise measurements, which were previously difficult to obtain because we didn't have enough information about 204Tl, the element that comes before 204Pb.

The s-process branching points: the case of 204Tl
Stars create elements through a process called "nucleosynthesis." Sometimes, elements can change into different ones through a process called "beta decay."
Branching points: There are points in this process where an element can either capture a neutron or undergo beta decay. These are called "branching points."
Understanding branching points is crucial: The amount of each element produced depends heavily on how often it captures neutrons compared to how often it undergoes beta decay. This is influenced by conditions within the star, such as temperature and the number of neutrons available.
204Tl is a branching point: In the case of 204Tl, the uncertainty in how its beta decay rate changes with temperature, and the lack of experimental data on how easily it captures neutrons, made it difficult to accurately predict how much 204Pb is produced in stars.
Challenges of measuring radioactive elements: 204Tl is radioactive, making it challenging to study.
The n_TOF facility: This facility at CERN is well-suited for studying radioactive elements like 204Tl due to its high neutron flux.
The experiment: We successfully measured how 204Tl captures neutrons at the n_TOF facility, despite the challenges of working with a highly radioactive sample.

Impact of the new measurements: The new measurements significantly improved our understanding of how much 204Pb is produced in stars.