 The half @-@ lives of <unk> and <unk> are 90 years and 340 days , respectively . All the remaining radioisotopes have half @-@ lives that are less than 2 days , and the majority of these have half @-@ lives that are less than 48 seconds . Samarium also has five nuclear isomers with the most stable being <unk> ( half @-@ life 22 @.@ 6 minutes ) , <unk> ( t1 / 2 = 
