Chapter 2 - Lithium

Abstract

This chapter introduces lithium (Li). The cosmic abundance of lithium isotopes reflects primordial nucleosynthesis, galactic cosmic-ray spallation, and destruction processes. On Earth, the two isotopes are susceptible to separation in geological processes, due to their relatively large difference in mass. Lithium isotopic compositions of natural material therefore have important geochemical and cosmochemical implications. Lithium isotopes are also of interest to nuclear and biomedical sciences. One nuclear application is the use of Li as shielding material in nuclear reactors. In medical science, lithium is a therapeutic drug for manic depression. Despite considerable interest in lithium isotopes, applications in earth science and other disciplines have been seriously hampered by the intrinsic difficulty of precise measurement of low-mass isotopes. The relative mass difference between the two isotopes of lithium is about 16%, which is among the highest of thermally ionized elements. Isotopic fractionation during mass spectrometric and other instrumental analyses is severe and, in the absence of a third isotope, the effect of mass discrimination cannot be internally corrected.