Using a laser, chemists lead by Rainer Beck, Ecole Polytechnique Fédérale de Lausanne, Switzerland, have been able to excite the vibrational state and orientate methane molecules for chemisorption on a Ni(100) surface.
Their results show, contrary to statistical rate theory, methane’s reaction probability is not only controlled by the available (vibrational) energy but is electronic state-specific and sensitive to C–H stretch alignment.
An increase in methane reactivity of up to 60 % was observed when the laser polarization was parallel rather than normal to the surface. Excitation by the infrared laser prepares CH4 for reaction by placing it in a single rovibrationally excited state. This state has aligned angular momentum and vibrational transition dipole moment within the laboratory frame.
- Steric Effects in the Chemisorption of Vibrationally Excited Methane on Ni(100)
B. L. Yoder, R. Bisson, R. D. Beck
Science 2010, 329 (5991), 553 – 556.