Laser induced thermal desorption from surfaces

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Abstract
Nonresonant laser induced desorption of adsorbed molecules from surfaces has been simulated using the stochastic trajectory technique. An NO molecule is initially bound to a cold LiF(100) surface. Rapid heating of the surface is then simulated via random forces applied to the edges of the 32 atom surface slabs. When the rate of heating is rapid compared to the rates of thermalization of the degrees of freedom of the molecule, it is found that the mean energies of the translational, rotational, and vibrational degrees of freedom of the desorbing molecule are significantly lower than those corresponding to the temperature of the surface at the instant of desorption. Additionally, the angular distribution of the desorbing molecules is found to peak towards the surface normal, and the rotational angular momentum vector is preferentially aligned parallel to the surface plane. These results shed light on recent experimental observations.