C&EN: IT'S ELEMENTAL: THE PERIODIC TABLE

CALIFORNIUM

JYLLIAN KEMSLEY , C&EN WEST COAST BUREAU

CALIFORIUM AT A GLANCE

Name: Named after the state of California.

Atomic mass: (251).

History: Produced in 1950 by Stanley G. Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg at the University of California, Berkeley, by using a cyclotron to bombard curium-242 with -particles.

Occurrence: Artificially produced.

Appearance: Silvery metal.

Behavior: Radioactive and a very strong neutron emitter.

Uses: Used as a portable neutron source in core analysis in drilling oil wells and for the discovery of metals such as gold and silver. The californium-252 isotope is used in cancer therapy.

When I look back to the discovery of californium--and the othertransuranium elements discovered in Berkeley in the 1940s and 1950s--I get a feeling for the glorious days those must have been. As the arms race and Cold War all but guaranteed funding for nuclear chemistry, Glenn T. Seaborg and colleagues created element after element. The University of California (UC) was the jewel of state university systems, envied across the country. The Radiation Laboratory (now Lawrence Berkeley National Laboratory) founded by Ernest O. Lawrence became the first national laboratory.

Californium dreaming.

It was an exhilarating time, albeit with long days of hard, dangerous work. But a century after the Gold Rush, this was a different kind of elemental quest. In some ways, the scientists were looking for substances more precious than gold--atoms predicted to exist, but never observed. Instead of a pan and magnifying glass, they used a cyclotron and a separation column. The danger lay not in rock slides but in radiation exposure.


	WIZARDS Nuclear scientists Thompson (left) and Seaborg pose as old-time alchemists in 1948, shortly before their discovery of californium at UC Berkeley.
	COURTESY OF LAWRENCE BERKELEY NATIONAL LABORATORY

Isolating "eka-dysprosium" (the first name for californium, the actinide analog of dysprosium) took thought and careful experiments. The approach taken by Stanley G. Thompson, Kenneth Street Jr., Albert Ghiorso, and Seaborg involved bombardment of curium with helium ions [Phys. Rev., 80, 790 (1950)]. The first challenge was to obtain enough curium, a process involving "tedious chemical separations." The paper notes that accurate prediction of the new element's nuclear properties was essential to get the bombardment, element separation, and radioactivity measurements correct. "An erroneous prediction of any of these properties would have meant unsuccessful experiments," the authors wrote. They clearly built upon prior knowledge, crediting berkelium's discovery as being of "primary importance" for predicting the properties of californium.

It was a group effort involving several different disciplines. Thompson, Street, and Seaborg were chemists, but Ghiorso was an electrical engineer. A California native, Ghiorso was introduced to Lawrence's "Rad Lab" in 1940 through a contract to build a communication system for the secretaries, but a year later he was reengineering Geiger-Müller counters, and within five years he was developing new methods to detect radiation--including the -particles of californium. Scientists behind the scenes played critical roles as well. In his 1951 Nobel address, Seaborg took the time to credit Nelson Garden and the Health Chemistry Group at the laboratory for "the successful handling in a safe manner of the huge amounts of radioactivity in the targeted material." Those who groan at the thought of interacting with their current health and safety departments should take heed.

But my venture into history and the heady days at Berkeley is accompanied by a twinge of sadness. The once magnificent UC seems to be faltering. Today, its faculty members are concerned about the health of the system in the face of cyclical state budget problems--chemistry departments have barely recovered from cuts in the early 1990s, only to be faced again this year with the repercussions of a massive state budget shortfall. Meanwhile, the ratio of graduate to undergraduate students is decreasing, leading one chemistry department chairman to fret that UC and the state are not supporting graduate education like they did 30--or 60--years ago. UC has also been loudly criticized for its management of Los Alamos National Laboratory. It's a sad state of affairs for the system honored with the elements berkelium and californium.

The situation is not entirely bleak, however. Since 1995, UC faculty have earned four Nobel Prizes in chemistry and one in physics. In the 2002 U.S. News & World Report ranking of graduate schools, UC Berkeley placed first for chemistry and second for physics. Whatever problems California may have, UC is still attracting the best and the brightest in the physical sciences.

So perhaps the californium legacy lives on at UC, in the detection of the neutrino, understanding of the enzymatic synthesis of ATP, and discovery of conductive polymers as much as in nuclear chemistry. Ghiorso himself is still working on accelerators. His tenth is a small one, intended for use in a classroom or hospital. "I really should be retired and not doing anything," he says. "At this age, you're supposed to just read your reprints." But the excitement of research continues to draw him back to the lab, just as it inspires the rest of us.

Jyllian Kemsley, a science writer based in San Jose, Calif., was a 2003 summer intern at Chemical & Engineering News. She lived in California during her teens and returned for graduate school, although she attended the school on the other side of the Bay from Berkeley.

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