Polar- and azimuth-angle-dependent rotational and vibrational excitation of desorbing product CO2 in CO oxidation on palladium surfaces

Clear polar and azimuth angle dependencies were found in rotational and vibrational energies of product CO2 in CO oxidation on Pd surfaces. On Pd(110)-(1x1), with increases in polar angle, both energies decreased in the 001] direction but remained constant in 110]. On the Pd(110) with missing rows, both energies increased in 001] but decreased in 110], indicating that the transition state changes with the geometry of the substrate. On Pd(111), the rotational energy greatly increased, but the vibrational energy decreased. Such angular dependence of internal energy provides new dimensions in surface reaction dynamics.