At the center of this work are the first mass measurements of three extremely neutron-rich tin isotopes: tin-136, tin-137 and tin-138. The results are published in the journal Physical Review Letters.

Some elements have more than one stable (nonradioactive) isotope—variants of the same substance, but with different numbers of neutrons in their atomic nuclei that alter the mass. (The element's ...

Nuclei with varying numbers of neutrons are called isotopes of an element. So, isotopes of iron include iron-54 with 26 protons and 28 neutrons, iron-56 with 26 protons and 30 neutrons, and iron ...