Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Physical Chemistry

Quantum Description Of Two-Molecule Collisions

New experiments probe dynamics with unprecedented detail

by Elizabeth K. Wilson
November 27, 2012 | A version of this story appeared in Volume 90, Issue 48

[+]Enlarge
Credit: Ludwig Scharfenberg
A Stark decelerator controls a beam of HO∙ radicals, which collide with a beam of NO∙ radicals.
Photograph of the Strak decelerator, which controls a beam of hydroxyl radicals.
Credit: Ludwig Scharfenberg
A Stark decelerator controls a beam of HO∙ radicals, which collide with a beam of NO∙ radicals.

To understand phenomena such as combustion and atmospheric chemistry, scientists need to know quantum state dynamics of atomic and molecular scattering. But such descriptions tax even modern computers and experimental methods. Until now, the most complex type of collision scientists have been able to characterize is that of a homonuclear diatomic molecule such as H2. But in a new experiment, theorist Gerrit C. Groenenboom and experimentalist Sebastiaan Y. T. van de Meerakker of Radboud University Nijmegen and colleagues have probed the dynamics of collisions between two diatomic radicals—HO∙ and NO∙—something that computers still can’t do in detail (Science, DOI: 10.1126/science.1229549). The group collided beams of the radicals and observed their rotational and spin-orbit inelastic scattering cross sections. To the researchers’ surprise, they found that the experimental results agreed well with predictions of a relatively simple theoretical model that only treats long-range interactions and avoids the extreme complexity of close-range effects. Until computational power catches up, this simple theoretical treatment could be used to explore other complicated collisions involving radicals that play a vital role in areas such as astrochemistry.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.