20 Ne Ne Ne

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1 Stable isotope Relative atomic mass Mole fraction 20 Ne Ne Ne Neon isotopes in Earth/planetary science Neon is subject to stable isotopic fractionation by physical processes such as exchange between gas, liquid, and solid phases. Small variations in the isotope-amount ratio n( 22 Ne)/n( 20 Ne) have been used to examine gas-liquid exchange processes during groundwater recharge (water moving downward from the surface) and discharge [17, 93-96]. Neon isotopes in geochronology 21 Ne and 22 Ne have nucleogenic (produced by a natural terrestrial nuclear reaction, not a reaction beginning with cosmic rays) components that form in the Earth s crust largely by reactions of 18 O and 19 F in minerals with neutrons and alpha particles emitted from uranium and thorium decay. In addition, neon isotopes can form at the surface of the Earth and in extraterrestrial bodies by cosmic-ray-induced spallation reactions on magnesium, silicon, aluminum, and sodium. Analyses of all 3 stable neon isotopes may be used to distinguish these sources from primordial neon. The relative amounts of atmospheric neon and crustal nucleogenic neon isotopes in deep groundwaters and natural gases can be used in studies of solid-water-gas interactions and migration (Figure 1). The cosmogenic component is mainly detected in 21 Ne and can be used to determine cosmic-ray exposure ages of rock samples, including meteorites

2 exposed during travel through space and boulders exposed by melting of glacial ice (Figure 1) [17, 93-95]. Fig. 1: Neon-isotope ratios of water from fractures in quartzite (open diamonds) and water from fractures in vein quartz (solid circles) from the deep gold mines of the Witwatersrand Basin, South Africa [97]. The mole ratio n( 21 Ne)/n 22 Ne) depends upon the ratio of oxygen to fluorine in the ~40 μm reaction range of alpha particles from uranium and thorium. Lippmann-Pipke et al. [97] show that the neon end-member represents a fluorine-depleted fluid component that was trapped in fluid inclusions in vein quartz more than two billion years ago.

3 Neon isotopes in industry Masers (Microwave Amplification by Stimulated Emission of Radiation) containing 20 Ne have been used to study quantum physics. 21 Ne may also play a role in maser studies of quantum physics [98, 99]. Neon isotopes used as a source of radioactive isotope(s) 22 Ne is used to produce radioisotope 22 Na via the reaction 22 Ne (p, n) 22 Na [98, 100, 101]. 20 Ne can be used to produce radioisotope 18 F via the reaction 20 Ne (d, 4 He) 18 F [98, 101].

4 Glossary alpha particle a positively charged nuclear particle identical with the nucleus of a helium atom consisting of two protons and two neutrons. [return] atomic number (Z) The number of protons in the nucleus of an atom. chondrites (or chondritic meteorites) non-metallic meteorites which have not undergone compositional change due to melting because they were part of primitive asteroids, and thus reflect the composition of the solar nebula from which our Solar System formed. cosmogenic produced by the interaction of Earth materials (soil, rock, and atmosphere) and meteorites with high-energy cosmic rays, resulting in protons and neutrons to be expelled from an atom (termed cosmic ray spallation). [return] cosmic rays extremely high-energy radiation, mainly originating outside the Solar System, consisting of one or more charged particles, such as protons, alpha particles, and larger atomic nuclei. [return] electron elementary particle of matter with a negative electric charge and a rest mass of about kg. element (chemical element) a species of atoms; all atoms with the same number of protons in the atomic nucleus. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus [703]. gamma rays (gamma radiation) a stream of high-energy electromagnetic radiation given off by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher than those of X-rays; thus, gamma rays have greater penetrating power. half-life (radioactive) the time interval that it takes for the total number of atoms of any radioactive isotope to decay and leave only one-half of the original number of atoms. isotope one of two or more species of atoms of a given element (having the same number of protons in the nucleus) with different atomic masses (different number of neutrons in the nucleus). The atom can either be a stable isotope or a radioactive isotope. isotope ratio (R) number (symbol N) of atoms of one isotope divided by the number of atoms of another isotope of the same chemical element in the same system [706]. [return] isotope-amount ratio (r) amount (symbol n) of an isotope divided by the amount of another isotope of the chemical element in the same system [706]. [return] isotopic fractionation (stable-isotope fractionation) preferential enrichment of one isotope of an element over another, owing to slight variations in their physical, chemical, or biological properties [706]. [return]

5 meteorite a meteoroid that has survived atmospheric passage and fallen to the Earth s surface in one or more recoverable fragments. See also chondrites [705]. [return] neutron an elementary particle with no net charge and a rest mass of about kg, slightly more than that of the proton. All atoms contain neutrons in their nucleus except for protium ( 1 H). [return] proton an elementary particle having a rest mass of about kg, slightly less than that of a neutron, and a positive electric charge equal and opposite to that of the electron. The number of protons in the nucleus of an atom is the atomic number. radioactive decay the process by which unstable (or radioactive) isotopes lose energy by emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma radiation, neutrons or protons to reach a final stable energy state. radioisotope (radioactive isotope) an atom for which radioactive decay has been experimentally measured (also see half-life). [return] solar nebula the cloud of dust and gas from which the solar system is believed to have condensed, mainly by gravitational attraction about 4.5 billion years ago. spallation a process in which fragments of a solid (spall) are ejected from the solid due to impact or stress. In nuclear physics, spallation is the process in which a nucleus of a heavy element emits a large number of nucleons (isotopes) as a result of being hit by a high-energy particle (e.g., a cosmic ray), resulting is a substantial loss of its atomic weight. [return] stable isotope an atom for which no radioactive decay has ever been experimentally measured. X-rays electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers shorter than those of UV rays and typically longer than those of gamma rays. References 17. M. Ozima, and Podosek, F.A. Noble Gas Geochemistry: 2nd Edition. Cambridge University Press (2002). 93. Noble gases in Geochemistry and Cosmochemistry: Reviews in Mineralogy and Geochemistry. Mineralogical Society of America and the Geochemical Society, Washington, D.C. (2002). 94. T. E. Cerling, and Craig, H. Annual Review of Earth and Planetary Sciences. 22 (1), 273 (1994). 95. D. Lal, and Peters, B. In Cosmic Rays II (K. Sitte, ed.), pp Springer-Verlag., New York (1967). 96. F. Peeters, U. Beyerle, W. Aeschbach-Hertig, J. Holocher, M. S. Brennwald, and R. Kipfer. Geochimica et Cosmochimica Acta. 67 (4), 587 (2003).

6 97. J. Lippmann-Pipke, B. Sherwood Lollar, S. Niedermann, N. A. Stroncik, R. Naumann, E. van Heerden, and T. C. Onstott. Chemical Geology. 283 (3-4), 287 (2011). 98. T. S. I. Inc. Neon Isotopes. Trace Sciences International Inc Feb W. R. Bennett. Physical Review. 126, 580 (1962) M. J. Winter, The University of Sheffield and WebElements Ltd. Neon. The University of Sheffield and WebElements Ltd Feb R. Policroniades, Moreno, E., Varela, A., Murillo, G., Huerta, A., Ortiz, M.E., and Chávez, E. Revista Mexicana De Fisica S. 54 (1), 46 (2008) I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Blackwell Scientific Publications, Oxford (1997) American Geological Institute Glossary of Geology. American Geosciences Institute, Alexandria, Virginia (2011) Coplen. Rapid Communications in Mass Spectrometry. 25 (2011).