Energy exchange between adsorbate AND SURFACE

FIGURE 3.11. Chemiluminescence in the CO oxidation on a Pd(llO) surface [46]. (a) Average vibrational and rotational temperatures of CO2 as a function of the CO/O2 ratio at Tg = 600K. (b) Temperatures of the antisymmetric and the bending vibrations of CO2 as a function of the CO/O2 ratio. 

330 meV—about the 10-fold thermal value given by the surface temperature [42]. The transition state is presumably bent while the product molecule is linear, and hence noticeable excitation of internal degrees of freedom is observed by IR chemiluminescence [43- 5]. As an example. Fig. 3.11 shows for a Pd(llO) surface the average vibrational and the rotational temperaturesas well as the temperatures of the asymmetric and the bending vibrations as a function of the CO/O2 ratio at a surface temperature of 600K [46]. These data indicate clearly that the asymmetric stretch vibration is considerably more excited than the other vibrational modes. 

FIGURE 3.12. Variation of the IR spectra from CO adsorbed at a Ru(OOOl) surface with surface temperature due to coupling of the stretch mode to that of frustrated rotation [47], 

Time-resolved SFG spectroscopy of CO/Ru(OOOi) Spectroscopic snapshots after heating the surface with a 110 fs laser pulse 

An harinonic coupling of CO stretch to frustrated translation leads to a transient redshift 

---