Mad physicists explode electrons.

With a year to go before the hundredth anniversary of the discovery of the electron, one team of physicists is hard at work devising fireworks for the celebrations. These researchers used electrons to create bubbles in liquid helium, then exploded the bubbles with sound waves.

"We see red flashes," says Humphrey J. Maris of Brown University in Providence, R.I., of the research described in the Sept. 2 Physical Review Letters.

Maris and his colleagues injected electrons into liquid helium, where the particles find themselves engaged in a shoving match. Helium atoms buffet the electrons, trying to keep them in place. However, each electron resists being pinned to any one position (SN: 5/25/96, p. 325) and surrounds itself with a 4-nanometer-wide bubble devoid of helium atoms.

"It sounds a bit like mad physicists at work," says Maris, "but we decided to blow the bubbles up." The researchers fired sound waves at a container of liq- uid helium holding millions of the bubbles. By abruptly raising and lowering the intensity of the sound, they rapidly varied the pressure within the liq- uid. Reducing the pressure made the bubbles expand. With "a large enough [reduction in pressure], the bubbles explode," says Maris. Each electron then escapes confinement with a flash of light.

Other physicists like the simplicity of using liquid helium to capture particles. "It's a very clever way to confine electrons," says Carlos R.

Stroud of the University of Rochester (N.Y.). He suggests that an array of such bubbles could store information in a quantum computer (SN: 1/20/96, p.38).

Maris is more impressed by his explosions than by any application of his group's method. "It really is an amazing thing to see something caused by a single electron."