A new molecule and a new signature. (Chemistry).

In a pair of discoveries, separate groups of researchers have identified a novel form of nitrogen and determined the spectroscopic signature of another curious molecule. Both molecules are unstable, making it difficult to create and study them.

Fulvio Cacace and his colleagues at the University of Rome "La Sapienza" created the novel form of nitrogen. Known as tetranitrogen, or [N.sub.4], the new molecule consists of two units of [N.sub.2]--the most common form of nitrogen molecule in air--connected by a long bond, the researchers report in the Jan. 18 Science.

Tetranitrogen is the first new polynitrogen molecule discovered or synthesized in about 50 years. The first, [N.sub.2], was identified in air in 1772. In 1956, the first molecules of [N.sub.3] were made in a laboratory. In the years since, chemists have been trying to make more polynitrogens.

It's not entirely an academic exercise. Tetranitrogen could open routes to new propellants and explosives, since calculations suggest that it releases a lot of energy as it breaks apart into two [N.sub.2] molecules, says Cacace.

In another report in the same Science, Bengt Nelander and Anders Engdahl of Lund University in Sweden have determined the infrared spectrum of the hydrogen-and-oxygen-containing molecule [H.sub.2][O.sub.3] --whose atoms line up H-O-O-O-H. Spectra derive from the vibrations of molecules' atoms and serve as fingerprints for molecules.

Although evidence that [H.sub.2][O.sub.3] could form first showed up in 1974, no one had identified the molecule's infrared spectrum until now. The signature should enable scientists to determine whether the molecule is present in Earth's atmosphere, says Nelander, who has been studying the interactions of small, stable molecules, such as water, with molecular fragments, such as OH and HOO, which are important participants in atmospheric chemistry. --J.G.