Fragment Mass Analyzer at the ATLAS facility of Argonne National Laboratory

Researchers used the Fragment Mass Analyzer at the Argonne National Laboratory’s ATLAS facility to monitor a radioactive element’s swift decay. Credit: Argonne National Laboratory

Atomic and molecular physics

A massive atom morphs with record-setting speed

An element’s swift radioactive decay confirms predictions about the behaviour of heavy nuclei.

An atom has been caught spitting out a fundamental nuclear particle in fewer than 18 nanoseconds, setting a speed record for a particular type of radioactive decay.

Many radioactive elements, including tellurium-104, emit ‘alpha particles’, which consist of two protons and two neutrons. Nuclear theory predicts that tellurium-104 should be extremely quick to emit an alpha particle, because doing so creates tin-100, which has an especially stable nuclear configuration. But tellurium-104’s decay to tin-100 is too rapid for current methods to observe directly.

Kalle Auranen at the Argonne National Laboratory in Lemont, Illinois, and his colleagues produced tiny amounts of the element xenon-108 and isolated them using the Fragment Mass Analyzer at Argonne’s ATLAS accelerator. They then watched for the emission of two alpha particles in succession, as xenon decayed first to tellurium-104 and then to tin-100.

The team determined that tellurium-104’s half-life is under 18 nanoseconds. The atom’s brief life span lends credence to models predicting that heavy nuclei composed of equal numbers of protons and neutrons should experience enhanced nuclear forces, leading to swift ejection of alpha particles.