Alliance of opposites: electrons and positrons make new molecule.
By soaking a silica sponge with antimatter antimatter: see antiparticle.
Substance composed of elementary particles having the mass and electric charge of ordinary matter (such as electrons and protons) but for which the charge and related magnetic properties are opposite in sign. , physicists have made the first matter-antimatter molecules. With further refinement, the technique might be used to briefly condense antimatter into fluid or solid states or even to create the first gamma-ray laser.
About 10 years ago, researchers created atoms of antihydrogen an·ti·hy·dro·gen
The antimatter equivalent of hydrogen.
The antimatter that corresponds to hydrogen. by combining antiprotons and positrons, the antimatter equivalents of protons and electrons. By itself, antihydrogen is as stable as hydrogen, though it's difficult to store in our matter world because of antimatter's propensity to vanish in a flash of gamma rays as soon as it comes into contact with matter.
For more than 50 years, however, physicists have been able to create nucleus-free "atoms" consisting of one electron and one positron. Attracted by their opposite charges, electrons and positrons will orbit each other, as the stars in a binary system do.
Unlike antihydrogen, however this unusual matter-antimatter hybrid, called positronium Positronium
An atomic-like system consisting of an electron and positron. Just as in the hydrogen atom, the energy levels of positronium are quantized, with the deepest levels bound by about 6.8 eV. , is unstable. It enjoys just a brief dance of death as the two particles spiral in toward mutual annihilation.
Still, positronium can live long enough--up to hundreds of nanoseconds--that physicists had speculated that the atoms might be able to pair up into molecules. Coaxing the atoms to do so would require assembling them in fight quarters and slowing them down enough to allow them to intermingle in·ter·min·gle
tr. & intr.v. in·ter·min·gled, in·ter·min·gling, in·ter·min·gles
To mix or become mixed together.
To perform this feat, David Cassidy and Allen Mills of the University of California, Riverside The University of California, Riverside, commonly known as UCR or UC Riverside, is a public research university and one of ten campuses of the University of California system. began by trapping millions of positrons--produced by a radioactive source--in an electromagnetic field. By applying brief electric pulses, the team expelled short bursts of positrons, directing them toward a thin, porous silica membrane. Inside the pores, some of the positrons scooped up electrons from the silica to form positronium.
The researchers hoped that some of the atoms would bounce around inside the pores and even temporarily stick to the pores' inner surfaces, where feeble electrostatic forces might slow them down and allow them to bind to to contract; as, to bind one's self to a wife s>.
See also: Bind each other as molecules.
All the positrons, whether free or bound in atoms or molecules, eventually annihilated, producing gamma rays. But Cassidy and Mills detected a telltale gamma-ray signal that they had expected the annihilation of molecular positronium to produce. For confirmation, they heated the membrane, creating conditions that would prevent the formation of molecules. Sure enough, the signal disappeared, the team reports in the Sept. 13 Nature. Mills says that the data show "all the hallmarks" of the appearance of positronium molecules.
Clifford M. Surko of the University of California, San Diego UCSD is consistently ranked among the top ten public universities for undergraduate education in the United States by U.S. News & World Report. It is a Public Ivy.  For graduate studies, most of UCSD's Ph.D. says that the evidence for the formation of positronium is convincing, if indirect. "I did not find any obvious potential flaw in it," he says.
This achievement is only the beginning, Mills says. If the researchers manage to concentrate more positrons into their sponge, more-complex states of matter states of matter, forms of matter differing in several properties because of differences in the motions and forces of the molecules (or atoms, ions, or elementary particles) of which they are composed. should appear. In a Bose-Einstein condensate, an exotic gas in which atoms share a quantum state, positrons could be forced to annihilate an·ni·hi·late
v. an·ni·hi·lat·ed, an·ni·hi·lat·ing, an·ni·hi·lates
a. To destroy completely: The naval force was annihilated during the attack. in sync to produce the first gamma-ray laser, Cassidy says. Even higher densities could lead to the first solid matter-antimatter state.