Isotopes of iodine iodine-123 and iodine-131 can also be seen by single photon emission computed tomography (SPECT) imaging. Iodine-124 is a proton-rich isotope of iodine with a half-life of 4.18 days. Its modes of decay are: 74.4% electron capture, 25.6% positron emission. I decays to Te. Iodine-124 can be made by numereous nuclear reactions via a cyclotron. The most common starting material used is Te. Iodine-124 as the iodide salt can be used to directly image the thyroid using positron emission tomography (PET). Iodine-124 can also be used as a PET radiotracer with a usefully longer half-life compared with fluorine-18 In this use,
Iodine with a spectroscopic Doppler-free technique while focusing on one of these lines, the hyperfine structure of the iodine molecule reveals itself. A line is now resolved such that either 15 components, (from even rotational quantum numbers, J), or 21 components (from odd rotational quantum numbers, J) are measurable. Elemental iodine is used as a disinfectant either as the element, or as the water-soluble triiodide anion I generated "in situ" by adding iodide to poorly water-soluble elemental iodine (the reverse chemical reaction makes some free elemental iodine available for antisepsis). Elemental iodine may also be used to treat iodine deficiency. In