Interaction of NO(v=12) with LiF(001): Evidence for anomalously large vibrational relaxation rates

We report direct measurements of the vibrational survival probability of NO(v=12) suffering collisions with a LiF(001) crystalline surface. Survival probabilities are near unity in all cases. At the lowest reported incidence energies (5.3 kJ/mol) and surface temperatures (290 K), vibrational relaxation is enhanced, angular distributions approach cos(θ), and rotational temperatures of the scattered molecules approach the surface temperature. At higher incidence energies, rotational temperatures are higher than the surface temperature and angular distributions narrow approaching cos6(θ). These results suggest that trapping desorption is occurring at least at the lowest incidence energies and surface temperatures. Substantial vibrational relaxation appears to occur when residence time are as small as a few ps. This is many orders of magnitude faster than has been reported for diatomic molecules relaxing from v=1 on salt crystals.