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A simple quantum dynamics problem?

Date:
July 15, 2010
Source:
American Institute of Physics
Summary:
New research 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.
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This is a step-by-step dissociation of Ne2Br2.
Credit: American Institute of Physics

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 Ne2Br2 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."


Story Source:

The above post is reprinted from materials provided by American Institute of Physics. Note: Materials may be edited for content and length.


Journal Reference:

  1. Jordan M. Pio, Molly A. Taylor, Wytze E. van der Veer, Craig R. Bieler, Jose A. Cabrera, Kenneth C. Janda. Real-time dissociation dynamics of the Ne2Br2 van der Waals complex. The Journal of Chemical Physics, 2010; 133 (1): 014305 DOI: 10.1063/1.3456550

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American Institute of Physics. "A simple quantum dynamics problem?." ScienceDaily. ScienceDaily, 15 July 2010. <www.sciencedaily.com/releases/2010/07/100714094617.htm>.
American Institute of Physics. (2010, July 15). A simple quantum dynamics problem?. ScienceDaily. Retrieved August 29, 2015 from www.sciencedaily.com/releases/2010/07/100714094617.htm
American Institute of Physics. "A simple quantum dynamics problem?." ScienceDaily. www.sciencedaily.com/releases/2010/07/100714094617.htm (accessed August 29, 2015).

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