Similar to a fingerprint atoms can be identified by their mass. It reflects even their “emotional state”, i.e. if and how much they are excited. This is due to the fact that the mass comprises – according to Albert Einstein’s famous equation E = mc2
– all building blocks and their interactions. Precise Penning trap mass measurements of short-lived nuclides, as performed with ISOLTRAP at CERN, therefore provide among others stringent tests of competing nuclear models as well as of the Standard Model of particle physics. Furthermore they extend our knowledge on stellar nucleosynthesis.