Calcium 41 in radiometric dating

Subject: Science and technology

Section: Nuclear technology

Concept :

Recent study shows that Calcium-41 can be used the same way as Carbon-14 in carbon dating, but with several advantages.

Radio Carbon Dating

Carbon-14 – Radiocarbon (Carbon 14) is an isotope of the element carbon that is unstable and weakly radioactive [The stable isotopes are carbon 12 and carbon 13]
It has a half-life of 5,700 years, so the technique can’t determine the age of objects older than around 50,000 years.
Radiocarbon dating – It is a method that provides objective age estimates for carbon-based materials that originated from living organisms.
Plants and animals assimilate Carbon 14 from carbon dioxide throughout their lifetimes.
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
An age could be estimated by measuring the amount of carbon-14 present in the sample.
There are 3 principal techniques used to measure carbon 14 content of any given sample.
Gas proportional counting
Liquid scintillation counting
Accelerator mass spectrometry (Advanced method)
The method was developed 1940s by Willard Libby, who received the Nobel Prize in Chemistry to this work in 1960.
The issue with carbon dating was to detect carbon-14 atoms, which occur once in around 1012 carbon atoms.

Calcium-41

Calcium-41 is a rare long-lived radio-isotope of Calcium that has a half-life of 99,400 years.
Calcium-41 is called a cosmogenic nuclide, because it is produced when cosmic rays from space smash into calcium atoms in the soil in a fission reaction, called spallation.
It is found in the earth’s crust, opening the door to dating fossilized bones and rock.
The issue is Calcium-41 is rarer, occurring once in around 1015 Calcium atoms.

How can the issue of detecting C-14 and CA-41 be resolved?

Atom Trap Trace Analysis (ATTA) – Researchers at the University of Science and Technology of China pitched a technique called atom-trap trace analysis (ATTA) to spot these atoms.
ATTA is both extremely sensitive and selective, and is based on the laser manipulation and detection of neutral atoms.
Procedure –
A sample is vaporised in an oven.
The atoms in the vapour are laser-cooled and loaded into a cage made of light and magnetic fields.
In ATTA, a laser’s frequency is tuned such that it imparts the same energy as required for an electron transition in Calcium-41.
The electrons absorb and release this energy, revealing the presence of their atoms.
Significance –
It can spot one calcium-41 atom in every 10 16 calcium atoms with 12% precision in seawater.
ATTA also avoids potassium-41 atoms, which are similar to calcium-41 atoms but lack the same electron transition.
It can also be modified to study isotopes of some noble gases that have defied techniques developed for carbon-14, such as argon-39, krypton-81, and krypton-85.

What are the applications of ATTA and Calcium-41?