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Science: Neutron Man

3 minute read

In June 1934 a distinguished Italian audience, including King Vittorio Emanuele, was told that Professor Enrico Fermi, theoretical and experimental physicist of the University of Rome, had artificially created a chemical element heavier than uranium.

Last week in Stockholm, the Swedish Academy of Sciences announced that this year’s Nobel Prize for Physics would go to Professor Fermi. This highest honor a physicist can win is worth more than $40,000 at current exchange rates.

Although the uranium atom was the most massive in the standard table of 92 elements, there was no theoretical reason why heavier elements should not exist.

Professor Fermi found them by bombarding uranium with a stream of neutrons (tiny particles which weigh about the same as a proton or hydrogen nucleus but have no electric charge). His bombarding neutrons slipped into the hearts of the uranium atoms, forming an unstable new element, ckarhcuium—No. 93. Similarly, in 1936, Dr. Fermi created a few atoms of ckaosmium—No. 94. Some of his other discoveries about neutrons: Having no electric charge, neutrons are not affected by the negative electric field outside an atom or by the positive charge on its nucleus. The only thing that stops them, or slows them down, is the mass of the nucleus itself. Hydrogen atoms are almost all nucleus, and so substances rich in hydrogen—such as paraffin and water—are effective neutron brakes. In 1935 Fermi wrote the equation for the slowing down of neutrons by hydrogen.

“Slow neutrons,” by one of those paradoxes which are common in atomic physics, make better bullets than fast neutrons for creating artificially radioactive substances. Having no electrical resistance to fight against, a slow neutron simply sidles up to an atom and “falls” into the nucleus—much as a slowly rolling golf ball drops into the cup whereas a faster one may roll by. Capture of a neutron makes an overweight, unstable atom which spits out particles or radiation or both. Fermi’s slow neutrons have induced this kind of radioactivity in more than 40 elements.

Born in Rome 37 years ago, Enrico Fermi was introduced to the atom at the University of Pisa, continued his acquaintance with it at Göttingen and Leyden, joined the University of Rome faculty in 1927. Short, wiry, dapper and cheerful, he has visited the U. S. several times, speaks heavily accented English, likes skiing, tennis. Some time ago Benito Mussolini, who is not insensitive to the prestige of Italian science, saw to it that Fermi got a fine new laboratory.

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