Physicists led by Joseph Hodges of the US National Institute of Standards and Time have created a device that can accurately determine the proportions of carbon-12 and carbon-13 in rock samples.
Carbon-12 and carbon-13 play a huge role in the study of the past of the planet since their content can be used to determine the age of fossils, bones, and other remains of ancient organisms.
In order to measure the fractions, the authors developed a system based on three different types of infrared lasers. The radiation frequency was chosen so that it interacted only with those carbon dioxide molecules that contained either carbon-12 or carbon-13. By illuminating a gaseous sample with a beam of these laser beams, their total mass and ratio in the sample can be determined very accurately.
Scientists have thus measured the fraction of carbon isotopes in ordinary air and in parallel determined them by classical isotopic analysis. They then used the same measurements to calculate the fraction of carbon isotopes in the Vienna PDB.
Because of this, they redefined the carbon isotope standard and linked it to two fundamental properties of carbon dioxide molecules, which have carbon-12 and carbon-13 atoms.
The authors hope that other isotopic standards will be redefined in the near future to make them easier to use.