Computer science blog



December 31, 2005, 7:02 PM CT

Breakthrough Inspired by Experiment

Breakthrough Inspired by Experiment
Need to understand the details of how a molecule is put together? Want to see the effects of the intricate dance that its electrons do to make a chemical bond? Try blowing a molecule to bits and calculating what happens to all the pieces. That's the approach taken by an international group of collaborators from the University of California at Davis, universities in Spain and Belgium, and the Chemical Sciences Division of the Department of Energy's Lawrence Berkeley National Laboratory.

When a hydrogen molecule, H2, is hit by a photon with enough energy to send both its electrons flying, the two protons left behind - the hydrogen nuclei - repel each other in a so-called Coulomb explosion. In this event, called the double photoionization of H2, the paths taken by the fleeing electrons have much to say about how close together the two nuclei were at the moment the photon struck, and just how the electrons were correlated in the molecule.

Correlation means that properties of the particles like position and momentum cannot be calculated independently. When three or more particles are involved, calculations are notoriously intractable, both in classical physics and quantum mechanics. In the 16 December, 2005 issue of Science the scientists report on the first-ever complete quantum mechanical solution of a system with four charged particles.........

Posted by: Jaison      Permalink


December 31, 2005, 2:59 PM CT

Turning Semiconducting Nanotubes Into Metals

Turning Semiconducting Nanotubes Into Metals
A new study, published in today's issue of the journal Science, finds that the basic electrical properties of semiconducting carbon nanotubes change when they are placed inside a magnetic field. The phenomenon is unique among known materials, and it could cause semiconducting nanotubes to transform into metals in even stronger magnetic fields.

Researchers found that the "band gap" of semiconducting nanotubes shrank steadily in the presence of a strong magnetic force, said lead researcher Junichiro Kono, an assistant professor of electrical and computer engineering at Rice University. The research, which involved a multidisciplinary team of electrical engineers, chemists and physicists, helps confirm quantum mechanical theories offered more than four decades ago, and it sheds new light on the unique electrical properties of carbon nanotubes, tiny cylinders of carbon that measure just one-billionth of a meter in diameter.

"We know carbon nanotubes are exceptionally strong, very light and imbued with wonderful electrical properties that make them candidates for things like 'smart' spacecraft components, 'smart' power grids, biological sensors, improved body armor and countless other applications," said paper co-author Richard Smalley, director of Rice's Carbon Nanotechnology Laboratory. "These findings remind us that there are still unique and wonderful properties that we have yet to uncover about nanotubes".........

Posted by: Jaison      Permalink