Xenon

The stable isotopes of xenon hold many clues about the formation of the elements, solar-system history, and Earth processes [29], [101]. For example, ¹²⁹Xe has been used as a detector of “extinct” radionuclides. Some ¹²⁹Xe is radiogenic as a result of being produced by the radioactive decay of ¹²⁹I (half-life of 1.7×10⁷ years). Because the half-life of ¹²⁹I is much smaller than the age of the Earth, primordial ¹²⁹I (i.e. that which was present at the beginning of Earth’s history) is essentially gone after it decayed to ¹²⁹Xe over geologic time. This means that radiogenic ¹²⁹Xe could be a marker of the former existence of the “extinct” isotope ¹²⁹I. Because primordial ¹²⁹I was produced largely in supernovae, detection of radiogenic ¹²⁹Xe in meteorites and terrestrial samples also implies that the time elapsed between ¹²⁹I supernova nucleosynthesis and planetary condensation was short compared to the subsequent history of the Solar System. The many isotopes and reaction mechanisms of xenon have contributed numerous insights into Earth processes through the study of “xenology” (xenon isotopic variations used as geodynamic tracers to study the dynamics of the Earth) [397].

Xenon isotopes are used in numerous ways to investigate the movement of inhaled gases in lungs and other parts of the body. If radioactive isotopes of xenon [ ¹²⁷Xe (with a half-life of 0.1 year), ¹³³Xe, and hyperpolarized (having non-equilibrium alignment of nuclear spins, suitable for magnetic resonance) ¹²⁹Xe] are inhaled, they can be tracked throughout the body by externally monitoring their decay products using magnetic resonance microscopy [high resolution magnetic resonance imaging (MRI) at microscopic (nanometer) levels] (Fig. IUPAC.54.2). This imaging technique is used to assess how well oxygen is taken up and transported by the blood [398].