The adsorption of methanethiol and n-propanethiol on the Au(111) surface has been studied by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-temperature scanning tunneling microscopy (LT-STM). Methanethiol desorbs molecularly from the chemisorbed monolayer at temperatures below 220 K in three overlapping desorption processes. No evidence for S-H or C-S bond cleavage has been found on the basis of three types of observations: (1) A mixture of chemisorbed CH3SD and CD3SH does not yield CD3SD, (2) no sulfur remains after desorption, and (3) no residual surface species remain when the adsorbed layer is heated to 300 K as measured by STM. On the other hand, when defects are introduced on the surface by ion bombardment, the desorption temperature of CH3SH is extended to 300 K and a small amount of dimethyl disulfide is observed to desorb at 410 K, indicating that S-H bond scission occurs on defect sites on Au(111) followed by dimerization of CH3S(a) species. Propanethiol also adsorbs nondissociatively on the Au(111) surface and desorbs from the surface below 250 K.

The angular and velocity distributions of desorbing products N2 and CO2 were studied in a steady-state NO + CO reaction on Pd(110) and Rh(110) by cross-correlation time-of-flight techniques. The CO2 desorption sharply collimated along the surface normal on both surfaces. On the other hand, N2 desorption on Pd(110) sharply collimated along about 40° off the surface normal in the plane along the [001] direction below around 650 K, yielding a translational temperature of about 3600 K. At higher temperatures, the normally directed desorption was relatively enhanced. On Rh(110), desorbing N2 sharply collimated along the surface normal, yielding a translational temperature of about 2500 K. The inclined desorption was assigned to the decomposition of the intermediate, N2O(a) → N2(g) + O(a), and the normally directed component was proposed to be due to the associative desorption of adsorbed nitrogen atoms, 2N(a) → N2(g). The branching of these pathways was analyzed on Pd(110).

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The decomposition of N 2 O(a) was studied on Rh(110) at 95-200 K through the analysis of the angular distributions of desorbing N 2 by means of angle-resolved thermal desorption. N 2 O(a) was highly decomposed during the heating procedures, emitting N 2 (g) and releasing O(a). N 2 desorption showed four peaks, at 105-110 K (β 4 -N 2 ), 120-130 K (β 3 -N 2 ), 140-150 K (β 2 -N 2 ), and 160-165 K (β 1 -N 2 ). The appearance of each peak was sensitive to annealing after oxygen adsorption and also to the amount of N 2 O exposure. The β 1 -N 2 peak was major at low N 2 O exposures and showed a cosine distribution. On the other hand, β 2 -N 2 and β 3 -N 2 on an oxygen-modified surface revealed inclined and sharp collimation at around 30°off the surface normal in the plane along the [001] direction, whereas β 4 -N 2 on a clean surface collimated at around 70°off the surface normal, close to the [001] direction. An inclined or surface-parallel form of adsorbed N 2 O was proposed as the precursor for inclined N 2 desorption.