Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Kinetic isotope effect effects to be easily measured and interpreted. In contrast, secondary effects are generally very small for heavier elements and close in magnitude to the experimental uncertainty, which complicates their interpretation and limits their utility. In the context of isotope effects, "hydrogen" is frequently used to refer to the light isotope, protium (H), specifically. In the rest of this article, reference to "hydrogen" and "deuterium" in parallel grammatical constructions or direct comparisons between them should be interpreted as referring to protium and deuterium. The theory of kinetic isotope effects was first formulated by Jacob Bigeleisen in 1949. Bigeleisen's general formula for