In 1994 an international research team led by Peter Armbruster and Sigurd Hofmann at the Institute for Heavy Ion Research at Darmstadt, Germany bombarded bismuth-209 atoms with nickel-64 ions. In an 18-day experiment, three atoms were unambiguously identified as an isotope of element 111 with mass number 272 and a half-life of 1.5 msec. The discovery was officially confirmed in 2003, and the discoverers named the element in honor of Wilhelm Conrad Roentgen. The most stable isotope, roentgenium-280, has a half-life of approximately 3.6 sec.
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