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A Simple Quantum Dynamics Problem?

15.07.2010
Research reported in The Journal of Chemical Physics, which is published by the American Institute of Physics, provides the first real-time measurements of the time dependence of the individual steps of dissociation of a complex consisting of two rare gas atoms and a halogen molecule.

"The goal of this work is to provide a test case for quantum dynamics theory," says author Kenneth C. Janda of the University of California, Irvine. "It is a problem that is easy, but not too easy, in the sense that a fundamental quantum dynamics explanation is within reach."

Researchers cooled a mixture of helium, neon, and bromine by spraying it through a nozzle, resulting in a stream of gas particles traveling at the same speed. This created a very low temperature in a moving frame of reference -- the particles were stationary relative to one another and condensed to form Ne(2)Br(2) tetrahedral complexes. After the bromine molecule was excited with a laser pulse, the dissociation of the complex over a period of tens of picoseconds was observed spectroscopically. Adding 16 quanta of vibrational energy to the bromine-stretching vibration resulted in rapid direct dissociation. The two Ne atoms dissociated without interacting with each other. However, with slightly higher vibrational excitation, a 23-quanta boost, the bromine anharmonicity led to sharing of the kinetic energy between the Ne atoms and a much more complicated dissociation mechanism.

"For 23 quanta, the first transfer of vibration fails to knock off one of the neon atoms 80 percent of the time," says Janda. "Instead a tiny liquid drop is formed, allowing a neon atom to move in a direct line with the bromine atoms. The next vibration shoots it off like a pool stick hitting the cue ball."

The article "Real-time dissociation dynamics of the Ne2Br2 van der Waals complex" by Jordan M. Pio, Molly A. Taylor, Wytze E. van der Veer, Craig R. Bieler, Jose A. Cabrera, and Kenneth C. Janda was published online in The Journal of Chemical Physics on July 7, 2010. See: http://link.aip.org/link/JCPSA6/v133/i1/p014305/s1

Journalists may request a free PDF of this article by contacting jbardi@aip.org

NOTE: An image is available for journalists. Please contact jbardi@aip.org

Figure Caption: "Step-by-step dissociation of Ne2Br2."

ABOUT THE JOURNAL OF CHEMICAL PHYSICS
The Journal of Chemical Physics publishes concise and definitive reports of significant research in methods and applications of chemical physics. Innovative research in traditional areas of chemical physics such as spectroscopy, kinetics, statistical mechanics, and quantum mechanics continue to be areas of interest to readers of JCP. In addition, newer areas such as polymers, materials, surfaces/interfaces, information theory, and systems of biological relevance are of increasing importance. Routine applications of chemical physics techniques may not be appropriate for JCP. Content is published online daily, collected into four monthly online and printed issues (48 issues per year); the journal is published by the American Institute of Physics. See: http://jcp.aip.org/
ABOUT AIP
The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

Jason Socrates Bardi | Newswise Science News
Further information:
http://www.aip.org

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