Trapping-desorption energy distribution

Fig. 9. Incidence energy dependence of the vibrational state population distribution resulting when NO(u = 12) is scattered from LiF(OOl) at a surface temperature of (a) 480 K, and (b) 290 K. Relaxation of large amplitude vibrational motion to phonons is weak compared to what is possible on metals. Increased relaxation at the lowest incidence energies and surface temperatures are indicators of a trapping/desorption mechanism for vibrational energy transfer. Angular and rotational population distributions support this conclusion. Estimations of the residence times suggest that coupling to phonons is significant when residence times are only as long as ps. (See Ref. 58.)...

FIGURE 3.10. Scattering of NO from an oxidized Ge surface [37]. (a) Time-of-flight distributions of the incident and scattered molecules in various rotational states ]". (b) Correlation between the mean translational and the rotational energy for molecules undergoing direct inelastic scattering (a) and trapping desorption (b). 

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