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17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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New Type of Nuclear Decay Demonstrated
8 January 2001 7:00 pm
Physicists predicted democracy--in atomic decay--but researchers have caught neon atoms doing something that might turn out to be very undemocratic. If they are correct, they will have discovered a new form of nuclear decay, and given scientists a powerful way of investigating the structure of the nucleus.
Radioactive nuclei are unstable by nature, and they perform all kinds of tricks to settle down. For instance, they might spit out a helium nucleus (also known as an alpha particle) or a proton. In some cases, a nucleus may wish to spit out two protons. There are several ways physicists imagine this can happen. The nucleus can emit a single proton and then a second in rapid succession, or it can emit them both at the same time--a process dubbed "democratic decay" by the Soviet theorists who predicted it. Strangest of all, it ought to be able to spit out a bound packet of two protons--essentially a helium-2 nucleus, which is never spotted in nature. The helium-2 nucleus then splits into two separate protons.
To try to demonstrate that helium-2 decay can exist, physicist Alfredo Galindo-Uribarri of Oak Ridge National Laboratory in Tennessee and colleagues smashed a stream of fluorine-17 into a hydrogen-rich target. When a fluorine atom hit a hydrogen (which is just a proton) hard enough, the fluorine-17 became neon-18--the nucleus the researchers were hoping to study. Neon-18 cannot emit one proton at a time, because it's forbidden by quantum theory. But it can lose two protons at a time. Thus, neon-18 must decay either via democratic decay or by emitting a helium-2, the team reports in the 1 January issue of Physical Review Letters.
"I think the result is really quite exciting," says Philip Woods, a nuclear physicist at the University of Edinburgh, particularly because the data suggest that the helium-2 decay is going on, rather than democratic decay. If the results hold up, "... it would allow us, in theory, to understand better phenomena within the nucleus," says Bertram Blank of the Center for Nuclear Studies in Bordeaux-Gradignan, France, including how protons inside the nucleus pair up.