REFERENCE SITE----
 
  About LENRs
  Investigations

Researchers Probe Chemistry of Bubbles
By Daniel S. Burgess
Photonics Technology News

September 2002

Since luminescence in single cavitating bubbles was described more than a decade ago, the phenomenon has attracted much attention from scientists. Earlier this year, interest was piqued all the more, when a team at Oak Ridge National Laboratory in Tennessee claimed to have observed neutron emissions from the bubbles that indicated fusion processes. Now researchers at the University of Illinois at Urbana- Champaign have analyzed the chemistry of single bubbles, opening the door to a better understanding of the event and calling into question the claims of fusion. Sonoluminescence occurs in the bubbles in an acoustic wave in a liquid. In a low-pressure region of the wave, a bubble expands a thousandfold, trapping gases that were dissolved in the liquid. When exposed to a high-pressure region, the bubble collapses violently, producing temperatures that may be as high as 20,000 K and ionizing the gases within.

At this stage, it emits a 50- to 500-ps pulse of broadband radiation, and the products of the reaction dissolve back into the liquid. The process begins again as the bubble is exposed once more to a low-pressure region of the wave.

The university researchers created their 60-m-diameter bubbles in a 15-ml glass cell that contained water at 3 or 22C. A titanium rod vibrating at 28 or 52 kHz induced the acoustic waves, and a Jobin Yvon monochromator and a 1024 X 256-pixel CCD detector collected the spectra from individual cavitating bubbles. The team employed a long-pass filter at wavelengths longer than 400 nm to minimize second-order radiation.

Energy conversion

The scientists monitored the production of ions, radicals and photons in a given collapse event. Together with measurements of the size of the bubbles, these counts enabled them to estimate the efficiency with which a bubble converts its potential energy into mechanical energy, heat, chemical reactions and light.

They discovered that about 1/10,000 of the energy in a collapsing bubble was used to form nitrite ions and hydroxyl radicals from the nitrogen that diffused into it in the expansion phase. The energy of the photons released in luminescence was two orders of magnitude smaller. The results indirectly challenge the claim of fusion in perdeuterated acetone, noted Kenneth S. Suslick, who conducted the study with Yuri T. Didenko. The volatility of acetone should lead to strongly endothermic chemical reactions of polyatomic molecules in the bubbles that would readily consume the available energy and thereby limit the maximum temperature on collapse.

The researchers note, however, that the possibility of fusion by cavitation cannot be rejected in substances with extremely low volatility, such as polar organic liquids, liquid metals and molten salts.

 

(In accordance with Title 17, Section 107, of the U.S. Code, this material is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. New Energy Times has no affiliation whatsoever with the originator of the original text in this article; nor is New Energy Times endorsed or sponsored by the originator.)

"Go to Original" links are provided as a convenience to our readers and allow for verification of authenticity. However, as originating pages are often updated by their originating host sites, the versions posted on New Energy Times may not match the versions our readers view when clicking the "Go to Original" links.