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Carbon Dating with Lasers

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I. Galli et al., Phys. Rev. Lett. (2011) For a date, give me a ring. To determine the age of a sample, the SCAR technique uses a highly stable infrared laser to excite carbon dioxide molecules in a mirrored cavity. When the laser is turned off, trapped light dies away in the cavity (or “rings-down”) at a rate that depends on the amount of carbon-14 in the sample.

Phys. Rev. Lett. 107, 270802 (2011) [4 pages]
Molecular Gas Sensing Below Parts Per Trillion: Radiocarbon-Dioxide Optical Detection
I. GalliS. BartaliniS. BorriP. Cancio*D. MazzottiP. De Natale, and G. Giusfredi
Istituto Nazionale di Ottica-CNR (INO-CNR) and European Laboratory for Non-Linear Spectroscopy (LENS) Via N. Carrara 1, I-50019 Sesto Fiorentino, Italy

Radiocarbon (14C) concentrations at a 43 parts-per-quadrillion level are measured by using saturated-absorption cavity ringdown spectroscopy by exciting radiocarbon-dioxide (14C16O2) molecules at the 4.5  μm wavelength.
The ultimate sensitivity limits of molecular trace gas sensing are pushed down to attobar pressures using a comb-assisted absorption spectroscopy setup. Such a result represents the lowest pressure ever detected for a gas of simple molecules.
The unique sensitivity, the wide dynamic range, the compactness, and the relatively low cost of this table-top setup open new perspectives for 14C-tracing applications, such as radiocarbon dating, biomedicine, or environmental and earth sciences.
The detection of other very rare molecules can be pursued as well thanks to the wide and continuous mid-IR spectral coverage of the described setup.

Read more: physics.aps.org

Written by physicsgg

January 3, 2012 at 8:38 am

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