Iodine-125

Iodine-125 is a radioisotope of iodine which has uses in biological assays and in radiation therapy to treat prostate cancer and brain tumors. Its half-life is around 60 days and it emits gamma-rays with maximum energies of 35 keV, some of which are internally converted to x-rays. Iodine-125 is created by the electron capture decay of Xenon-125, which is a synthetic isotope of Xenon, itself created by neutron capture of the slightly radioactive Xenon-124, which occurs naturally with an abundance of around 0.1%. Because of the synthetic production route of Iodine-125 and its short half-life, the natural abundance is effectively 0%.

Physical Data

 * Element: Iodine
 * Z: 54
 * A: 125
 * Atomic Mass:
 * Density:
 * Physical state: Solid at room temperature
 * Isotopic abundance: 0%


 * Radioactive: Yes
 * T(1/2): 59.4 days
 * Decay: Electron capture to Tellurium-125
 * Emissions: Gamma-rays at 35.5 keV. 7% emitted, 93% internally converted to:
 * 27.0 keV (113% abundance relative to 7% gamm emission)
 * 31.0 keV (26%)
 * 27-32 keV (14%)
 * Half-value layer: 0.025 mm Pb