Stable Isotope
Definition
An isotope that does not undergo radioactive decay. Ratios of stable isotopes change only through physical or biological fractionation, such as evaporation or metabolic uptake, and record environmental conditions at the time of formation.
- Property
- Does not undergo radioactive decay
- Ratio changes via
- Physical or biological fractionation
- Example processes
- Evaporation, metabolic uptake
- Forensic role
- Records environmental conditions at formation
Common questions
How does a stable isotope differ from a radioactive isotope for forensic dating purposes?+
A radioactive isotope decays at a known rate and can be used to estimate elapsed time, whereas a stable isotope's ratio stays fixed once formed and instead encodes the environmental conditions, such as water source or diet, present at that time.
What kinds of forensic evidence commonly use stable isotope analysis?+
Hair, bone, nails, teeth, and plant or wood material are common substrates, since their isotope ratios can be compared against reference maps to narrow down a person's or an item's geographic origin or movement history.
Related terms
- Delta Notation (δ)
- A notation expressing the isotope ratio of a sample relative to an international standard in parts per thousand (per mil, ‰). Positive...
- Epsilon Notation (ε)
- Similar to delta but expressed in parts per ten thousand, used for radiogenic systems where variation is very small. Epsilon Nd and...
- MC-ICP-MS (Multi-Collector Inductively Coupled Plasma Mass Spectrometry)
- An instrument that ionises a liquid or laser-ablated sample in an argon plasma at about 8,000 K and simultaneously collects multiple ion...
- Radiogenic Isotope
- An isotope produced by radioactive decay of a parent nuclide over geological time. Its abundance in a rock or mineral increases predictably...
- TIMS (Thermal Ionisation Mass Spectrometry)
- An instrument that ionises a sample deposited on a metal filament and measures ion beam intensities with Faraday collectors. The gold standard...