Printer Friendly

Cold sliver may sense electron quiver. (Physics: from Seattle, at the American Physical Society's annual March meeting).

Using a sliver of material shaped like a diving board or cantilever, researchers have detected a force that's a billionth the strength of a typical chemical bond. At 800 zeptonewtons, it's the most sensitive measurement of mechanical force ever.

This exquisite sensitivity may finally make it possible to mechanically detect a single electron's magnetism, say Dan Rugar and John Mamin of IBM Almaden Research Center in San Jose, Calif.

Electrons and most nuclei act like tiny bar magnets because of a quantum mechanical property called spin. Sensing an electron's spin would be a coup for Rugar and his coworkers. They've long been developing a type of magnetic resonance imaging (MRO microscope for revealing identities and locations in solids of individual atoms--whose magnetism is much subtler than an electron's (SN: 6/11/94, p. 374). Since the early 1980s, scientists have used other types of microscopes to observe atoms by nonmagnetic means--but just on samples' surfaces. "If you can do 3-D imaging, that opens up a new vista," Rugar says.

The new microscope is designed to sense a magnetic force exerted when the spin of the particle repeatedly flips upside down in response to radio signals. To be detected, a spin must oscillate this way for a tenth of a second or so.

Estimates of the magnetic force exerted by a lone electron range from 1,000 to 10,000 zeptonewtons. Three years ago, Rugar's team built an instrument sensitive enough to detect forces as small as 7,000 zeptonewtons.

However, even the 4-kelvin temperature of that instrument still allowed excessive thermal vibrations in the cantilever. Those tremors cloaked the oscillations caused by an electron's magnetic force. The scientists operate their new microscope at a mere 40 millikelvins. To further reduce heating, they also use an extremely dim laser for measuring cantilever deflection.

By shaking the cantilever with a piezoelectric crystal, which changes shape when stimulated by electricity, the researchers found they could observe vibrations that flex the cantilever's end about 0.6 angstrom. That's less than the diameter of an atom and corresponds to the record-breaking value of 800 zeptonewtons.--P W.
COPYRIGHT 2001 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2001, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Science News
Date:Apr 7, 2001
Words:352
Previous Article:Oops! Tougher arsenic rule retracted. (Environment).
Next Article:Surface reaction recorded in real time. (Physics: from Seattle, at the American Physical Society's annual March meeting).


Related Articles
Physics: tiny world garners grand laurels.
High-precision tests in particle physics.
Ringing to a single proton's magnetic nudge.
Electron antics at magic angles.
Probing high-energy physics inside an atom.
Electrons in boxes: probing artificial atoms to stretch quantum physics.
Pushy lasers sweep into ion race.
Letters.
An electron runs through it: surprising rivulets and ripples complicate the microchip picture.
Comprehension.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters