DISCLAIMER: This article is being kept online for historical purposes. Though accurate at last review, it is no longer being updated. The page may contain broken links or outdated information.
Naduvalath, Balakrishnan Department of Chemistry, University of Nevada, Las Vegas, Nevada.
- Making of cold and ultracold molecules
- Ultracold chemistry
- Features of ultracold reactions
- Applications and future prospects
- Related Primary Literature
- Additional Reading
One of the long-standing goals in chemistry is to control and manipulate the outcome of chemical reactions to yield desired products. While some progress has been achieved in controlling product branching in photofragmentation of diatomic and triatomic molecules, the absolute control of bimolecular chemical reaction dynamics, even in simple atom-diatom exchange reactions (such as A + BC → AB + C or AC + B, where BC is the reactant molecule and AB and AC are possible product molecules), has yet to be realized. Precise control of molecular encounters and chemical reactions requires initial preparation of molecules in well-defined internal quantum states. However, at ordinary temperatures, molecules exist in a thermal population of internal quantum states, corresponding to different vibrational, rotational, and hyperfine levels. In typical diatomic molecules such as N2 or O2, the energy spacing between vibrational levels is on the order of a thousand kelvins (in this article, energy will be given as E/kB expressed in kelvins, where E is the kinetic energy and kB is the Boltzmann constant), the spacing between rotational energy levels is on the order of a few kelvins, and the spacing between hyperfine levels is a small fraction of a kelvin. The energy level separation becomes smaller for heavier molecules. To prepare molecules in specific internal quantum states, their translational temperature T (kinetic energy) must be reduced to significantly below 1 K so that the thermal energy kBT is smaller than the tiniest energy separation between internal quantum states. Thus, to enable control of reaction dynamics, molecules must be cooled to temperatures lower than a millikelvin or microkelvin, depending on their mass and energy-level structure.
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information