In recent years, however, a new class of isotope fractionation effects has been discovered in which this simple rule of mass dependency is violated. The discovery was made in an effort to explain the anomalous excess of the 17 O isotope in atmospheric CO, which has been observed at various air monitoring stations like Spitsbergen and the Canary Islands.
H is mass independent.
The extent of the mass-independent fractionation signal measured in the laboratory indeed is of the right magnitude to explain the atmospheric observations. The recently discovered isotope effect in CO has consequences of practical and more fundamental nature. Yet, OH belongs to the most elusive of all atmospheric species with a lifetime of only one second. Thus, better insight into the atmospheric budget of CO, and a better understanding of the OH distribution in the atmosphere may be obtained. Besides these useful applications of the discovered isotope effect, fundamental questions concerning reaction mechanisms in the gas phase are raised.