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Monday, February 15, 2010

Finding stable super heavy elements

There have been 90 elements found in nature. Some two dozen more have been created in labs. Most of these are so transitory they exist barely long enough for researchers to take note of the fact that they were created. However, some scientists believe that there is an island of stability in super heavy elements yet to be found.

To test this hypothesis, scientists needed to accurately measure the atomic mass of a super heavy element. By determining the exact mass of the element, the binding energy can be calculated, which in turn tells how stable the element can be, and leads to predictions of even larger stable elements. Up to this point, binding energies had only been inferred from decay rates.

Nobelium (element 102) was chosen for this purpose and produced by firing calcium ions onto lead foil with a particle accelerator. Michael Block and his international colleagues used the SHIP (Separator for Heavy Ion reaction Products) filter to separate out the nobelium ions, which were then sent on through the ‘Shiptrap’ facility to trap the ions and measure their atomic mass.

This experiment yielded two firsts: the first time a super heavy element had been trapped, and the first time the atomic mass of a super heavy element had been measured with extreme accuracy (the error rate was estimated to be about 5 millionths of one percent).

Predicted island of stability for super heavy elements, chart by Xanthine, 3/12/2006