Spatial distributions of desorbing products in steady-state NO and N2O reductions on Pd(110).
The angular and velocity distributions of desorbing product N(2) were examined over the crystal azimuth in steady-state NO+CO and N(2)O+CO reactions on Pd(110) by cross-correlation time-of-flight techniques. At surface temperatures below 600 K, N(2) desorption in both reactions splits into two directional lobes collimated along 41 degrees -45 degrees from the surface normal toward the [001] and [001] directions. Above 600 K, the normally directed N(2) desorption is enhanced in the NO reduction. Each product desorption component, as well as CO(2), shows a fairly asymmetric distribution about its collimation axis. Two factors, i.e., the anisotropic site structures and the reactant orientation and movements, are operative to induce such asymmetry, depending on the product emission mechanism.
Effect of co-adsorbed CO and reaction temperature on the dynamics of N2 desorption under steady-state N2O-CO reaction on Rh(110).
We have investigated the effect of co-absorbed CO and reaction temperature on the angular distribution of N(2) desorption by N(2)O decomposition under the steady state of N(2)O-CO reaction on Rh(110). Spatial distributions of desorbing product N(2) emission have been measured at various surface temperatures and CO coverages. The decomposed N(2) collimates at 48°-61° off normal in the parallel plane to [001] and [110] directions, indicating that adsorbed N(2)O just before the decomposition is oriented along the [001] direction. Although the inclined and collimated N(2) desorption is always observed at any steady-state CO coverage and reaction temperature, the shape of the collimated N(2) distribution varied dependent on the co-adsorbed CO coverage. The distribution becomes sharp and shifts toward the surface normal direction with increasing CO coverage. These effects of adsorbed CO on the angular distribution of N(2) are interpreted by the collision of desorbed N(2) with co-adsorbed CO.
Vibrational Spectra and Structure of Azomethane and Azomethane‐d6
The infrared spectra of gaseous and polycrystalline CH3NNCH3 and CD3NNCD3 have been recorded from 33 to 4000 cm−1. The corresponding Raman spectra of the liquid and solid samples have been measured from 100 to 4000 cm−1. The vibrational data provide definitive verification of a trans structure with C2h symmetry. A vibrational assignment is proposed for the 24 fundamental modes based upon the observed band contours, isotopic shift ratios, and group frequency correlations. The au and bg torsional modes were assigned to bands at 222 and 223 cm−1, respectively, and the internal rotational barrier of the methyl group was calculated to be ∼ 2.7 kcal/mole. A number of the internal fundamentals were observed to be split into doublets in the spectra of the solids which suggests that there are at least four molecules per unit cell in azomethane. The inversion center is apparently retained in the crystal since the rule of mutual exclusion was found to be operative.