Figure 1

Chemiluminescence measurements on Pd(110). (a)–(d) Infrared emission spectra at ${\mathrm{O}}_2/\mathrm{CO}=1/2$ and $T_{\mathrm{surf}}=600\mathrm{K}$. The resolution of the wave number is $4{\mathrm{cm}}^{-1}$. Intensities were normalized so that the maxima of peaks become unity. The thin lines show the emission spectra from AR product ${\mathrm{CO}}_2$ at $\theta =0°$ and $P=5.5\times {10}^{-2}\mathrm{Torr}$ (a), $\theta =40°$ in [001] and $P=5.5\times {10}^{-2}\mathrm{Torr}$ (b), $\theta =0°$ and $P=3.7\times {10}^{-3}\mathrm{Torr}$ (c), and $\theta =40°$ in [001] and $P=3.7\times {10}^{-3}\mathrm{Torr}$ (d). The thick solid lines show the best results of simulation. These were obtained with $T_{\mathrm{rot}}=700\mathrm{K}$ and $T_{\mathrm{vib}}=1400\mathrm{K}$ (a), $T_{\mathrm{rot}}=700\mathrm{K}$ and $T_{\mathrm{vib}}=1450\mathrm{K}$ (b), $T_{\mathrm{rot}}=950\mathrm{K}$ and $T_{\mathrm{vib}}=1500\mathrm{K}$ (c), and $T_{\mathrm{rot}}=550\mathrm{K}$ and $T_{\mathrm{vib}}=1200\mathrm{K}$ (d). For comparison, the best simulation at 0° and $P=3.7\times {10}^{-3}\mathrm{Torr}$ is shown by the broken line in (d). (e),(f) Comparison of experimental spectrum (smoothed) and some simulated curves. (g) Dependence on the reactant pressure on Pd(110): $T_{\mathrm{vib}}$ at $\theta =0°$ (open circles), $T_{\mathrm{vib}}$ at $\theta =40°$ ([001]) (closed circles), $T_{\mathrm{rot}}$ at $\theta =0°$ (open squares), and $T_{\mathrm{rot}}$ at $\theta =40°$ ([001]) (closed squares). Total exposure indicates the sum of ${\mathrm{O}}_2$ exposure and CO exposure and is proportional to $P$. Schematic illustration of Pd(110), polar angle $\theta$, and azimuthal directions is shown at the bottom of the left side.Reuse & Permissions

Figure 2

Angle dependence of the rotational and vibrational temperatures on Pd(110) and Pd(111). (a) Pd(110) at ${\mathrm{O}}_2/\mathrm{CO}=1/2$, $T_{\mathrm{surf}}=600\mathrm{K}$, and $P=3.7\times {10}^{-3}\mathrm{Torr}$. $T_{\mathrm{vib}}$ in $[1\overline{1}0]$ (open circles), $T_{\mathrm{vib}}$ in [001] (closed circles), $T_{\mathrm{rot}}$ in $[1\overline{1}0]$ (open squares), and $T_{\mathrm{rot}}$ in [001] (closed squares). (b) Pd(110) at ${\mathrm{O}}_2/\mathrm{CO}=2$, $T_{\mathrm{surf}}=600\mathrm{K}$, and $P=3.7\times {10}^{-3}\mathrm{Torr}$. $T_{\mathrm{vib}}$ in $[1\overline{1}0]$ (open circles), $T_{\mathrm{vib}}$ in [001] (closed circles), $T_{\mathrm{rot}}$ in $[1\overline{1}0]$ (open squares), and $T_{\mathrm{rot}}$ in [001] (closed squares). (c) Results on Pd(111) at ${\mathrm{O}}_2/\mathrm{CO}=1/2$, $T_{\mathrm{surf}}=700\mathrm{K}$, and $P=3.7\times {10}^{-3}\mathrm{Torr}$. The open circles and squares show $T_{\mathrm{vib}}$ and $T_{\mathrm{rot}}$. (d) Structures of the $\mathrm{Pd}(110)\mathrm{\text{−}}(1\times 1)$ surface and a proposed TS at ${\mathrm{O}}_2/\mathrm{CO}=1/2$. (e) Structures of Pd(110) with missing rows and a proposed TS at ${\mathrm{O}}_2/\mathrm{CO}=2$. An important point is that TSs are inclined in $y\mathrm{\text{−}}z$ and $x\mathrm{\text{−}}z$ planes on $\mathrm{Pd}(110)\mathrm{\text{−}}(1\times 1)$ and Pd(110) with missing rows, respectively. (f) Three O-C-O TSs with different inclination angles on a flat surface. These are simplified to be linear.Reuse & Permissions