<P> It has a half - life of 10.756 years and a maximum decay energy of 687 keV . It decays into stable , non-radioactive rubidium - 85 . Its most common decay ( 99.57 % ) is by beta particle emission with maximum energy of 687 keV and an average energy of 251 keV . The second most common decay ( 0.43 % ) is by beta particle emission ( maximum energy of 173 keV ) followed by gamma ray emission ( energy of 514 keV ) . Other decay modes have very small probabilities and emit less energetic gammas . There are 33 other known isotopes of krypton . </P>
krypton-85 decays by emission of a beta particle . the product of this decay is
stable , non-radioactive rubidium - 85