Fission fragments weighed

A team of scientists from the University of Jyväskylä in Finland has made high-precision mass measurements of 23 neutron-rich isotopes of strontium, zirconium, and molybdenum. The isotopes were produced as ions in proton-induced fission reactions of uranium. The researchers obtain a precision of about 10 keV by coaxing an isotopically clean ion bunch into a Penning trap—which combines a strong magnetic field with a static electric quadrupole field—where the ions’ mass can be deduced from the observed cyclotron motion in the magnetic field. The improved isotope masses provide information about nuclear binding energies and can reveal subtle effects in the complex structures of those nuclei. Astrophysicists, who consider how nuclei are built inside stars or novae, are also interested in the more precise data. (U. Hager et al  Phys. Rev. Lett.   96 , 042504, 2006  https://doi.org/10.1103/PhysRevLett.96.042504 .)