A new experimental technique uses state-resolved infrared laser excitation to probe a polyatomic molecule's dissociative chemisorption dynamics with previously unattainable detail. Methane molecules excited to $v=1\mathrm{}$ of the ${\nu }_3$ C-H stretching vibration are up to 1600 times more reactive on a clean Ni(100) surface than are molecules in the ground vibrational state. Over a translational energy range of 27 to 54 kJ/mol, their absolute reaction probability increases from $3\times {10}^{-4\mathrm{}}$ to $6\times {10}^{-3\mathrm{}}$, which indicates that ${\nu }_3$ is responsible only in part for the vibrational activation reported in previous studies.

• Received 26 March 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.868