Record-breaking laser technique detects gas at parts per quadrillion

Chemistry World ------ The accuracy of atmospheric gas detection has been significantly improved by researchers in China and the US. The team, led by Gerald Diebold, an expert in the photoacoustic effect at Brown University, were able to detect concentrations of gas at parts per quadrillion – a million billion. The photoacoustic effect is already the most practical and widely-used method for atmospheric pollutant detection, but until recently it was only possible to detect concentrations of gas down to parts per trillion. This made it difficult to detect trace pollutants in the atmosphere. At the most basic level, the photoacoustic effect occurs when a beam of light passes through a gas and is absorbed by the particles. This absorption causes the gas to expand, generating a pressure wave that can be detected as sound. The issue with this technique is that as the concentration of the particles in the air decreases, the strength of the signal also decreases until it can no longer be detected. To learn more click on the picture below to read the article.