Albert Ghiorso, 95; scientist helped discover 12 chemical elements
Wednesday, January 19, 2011; 8:29 PM
Albert Ghiorso, 95, an ingenious and inventive scientist who helped discover 12 chemical elements, an accomplishment perhaps unrivaled in the history of atomic research, died of undisclosed causes Dec. 26 at a care facility near his home in Berkeley, Calif.
Mr. Ghiorso had a bachelor's degree from the University of California at Berkeley but never received a doctorate. Yet, he worked for decades on research credited with pushing back the frontiers of the known world and vastly expanding the periodic table.
At one time, the chart of the elements appeared to end at uranium, No. 92. But Mr. Ghiorso forged on beyond them, creating elements that essentially could not be found on Earth.
All his groundbreaking work was carried out while he was a staff member at what is now the Lawrence Berkeley National Laboratory, which is managed by the University of California.
In the complex, challenging process of creating elements, Mr. Ghiorso was known for vital and innovative contributions at every stage. He developed the tools for creating new elements from those already known.
He also devised techniques for showing that the new elements had actually been created, even if the amounts were no more than a handful of atoms. In addition, he worked out methods for separating the new elements from their surroundings.
Nuclei include neutrons and protons, but the elements are identified by the number of protons, or positively charged particles. The nucleus of each element contains a unique number of protons. Hydrogen has just one, and uranium has 92.
Under carefully directed bombardment by smaller particles, produced in accelerators or nuclear reactors, heavy nuclei might undergo changes in structure or energy. Adding a proton to the nucleus transforms it into the nucleus of the next higher atomic number element. For instance, Mr. Ghiorso and collaborators were able to transform plutonium, which is atomic number 94, into americium, which is atomic number 95.
Apart from demonstrating the fruits of scientific skill and effort, the production of new elements has been seen as a means of learning more about the structure of matter and giving a glimpse of an earlier stage of the universe, in which such elements might have naturally existed. Some of the artificially created elements also have significant uses. For example, plutonium is used in atomic weaponry and americium is a critical component of smoke detectors.
Creating elements was a challenge.
"You had to be extraordinarily clever and careful," said Robert Schmieder, a former scientific collaborator who is working on a Ghiorso biography. "They were hard experiments."
One piece of equipment that Mr. Ghiorso devised was the multi-channel pulse-height analyzer. With it, seven elements were identified: americium, curium, berkelium, californium, einsteinium, fermium and mendelevium, said Schmieder. (Fermium is named for the celebrated Italian-born physicist; Mendelevium for the Russian who devised the periodic table.)