The curious case of germanium-72 An unusual isotope changes
phases as temperature rises As a rapidly rotating gemanium-72
nucleus gets hotter, pairing among the protons and neutrons
within the nucleus tends to decrease steadily. At one critical
temperature, however, the pairing spikes back up, as represented
in the center illustration. This odd behavior marks a phase
transition within the germanium-72 nucleus. (Illustration by
Andy Sproles, ORNL)(hi-res image) There's a lot we don't know
about the atomic nucleus, even though it was discovered a
century ago this year. We have, of course, learned much. We can
get energy by splitting the nucleus in a process known as
fission or smashing nuclei together in a process known as
fusion. While we can't say exactly when an unstable nucleus will
decay on its own—spontaneously transforming from one isotope to
another—we can say how fast a large group of nuclei will do so.
In fact, we can confidently determine the half-life of a
nucleus—the time in which 50 percent will d