The isotopes of oxygen are 16O (99.762% abundance), 17O (0.038%), and 18O
(0.200%). 17O has nuclear spin I = 5/2 and is an important nuclide for NMR
measurements. 18O is used as a tracer for tracking reagents or for the study of reaction
mechanisms. It is also useful for the assignment of absorption lines in infrared or Raman
spectra by means of isotope effects.