18O18

18O18 refers to a molecule composed of two oxygen atoms, each being the isotope oxygen-18 (18O). Oxygen-18 is a stable isotope of oxygen, meaning it does not undergo radioactive decay. It is heavier than the more common oxygen-16 isotope due to the presence of two additional neutrons in its nucleus. The natural abundance of oxygen-18 is approximately 0.20% compared to oxygen-16's 99.76%.

The molecule 18O18, also known as dioxygen-18 or O2-18, is therefore a form of molecular oxygen where both atoms are the heavier isotope. This molecular form can be produced through various enrichment processes that separate isotopes of oxygen. Its properties, such as bond length and vibrational frequencies, are very similar to normal oxygen (16O16) but are subtly different due to the increased mass.

18O18 finds applications in scientific research, particularly in areas where isotopic tracing is employed. For example, it can be used in studies of photosynthesis, respiration, and atmospheric chemistry to track the fate of oxygen atoms in different biological and chemical processes. Its use allows researchers to distinguish between oxygen originating from different sources or undergoing specific reactions. While not as common as naturally occurring oxygen, enriched 18O18 serves as a valuable tool for precise scientific investigations.