Discovery of Germanium 59
Ten years ago, a team of NSCL researchers discovered the then lightest known isotope of germanium: 60Ge. A recent NSCL experiment carried that work one step farther: to the discovery of an even more exotic, lighter germanium isotope – 59Ge. Researchers from the University of Warsaw in Poland led the recent work, assisted by NSCL collaborators. The discovery of these two isotopes offers a good glimpse into a decade of progress at the NSCL.
Why study these isotopes? Germanium 59 and 60 bump right up against the border between where germanium isotopes have enough neutrons or not for their 32 protons to stay together in a nucleus. Establishing the existence of such isotopes and studying their properties deepens our understanding of how protons and neutrons can interact to form matter.
The more exotic – in this case, the lighter – an isotope is, the fewer atoms of it get produced and the harder it is to find them. Thus, to succeed in the discovery of 59Ge, the researchers had to improve on the conditions used to find 60Ge.
The researchers prepared several “tricks” to optimize for the production of 59Ge and to make use of more cyclotron beam for the search. These included the use of an alternate target material to increase the production and the RF separator to filter out other isotopes. It turns out that neither of these options was needed – all that was required was using just the right A1900 fragment separator setting, including selection of the best combination of target and degrader to filter out other isotopes.
The crucial difference in the discovery of 59Ge compared to 60Ge was the experience that has been gained over 10 years to make full use of the A1900’s potential.