 Europium is produced by nuclear fission , but the fission product yields of europium isotopes are low near the top of the mass range for fission products . 
 Europium is produced by nuclear fission , but the fission product yields of europium isotopes <a href='drop_aux' title='1'><mark>are</mark></a>low near the top of the mass range for fission products . 
Europium is produced by nuclear fission , but da fission product yields of europium isotopes low near the top of the mass range for fission products .