Lifetimes of selective-adsorption resonances in atom-surface elastic scattering.

From a time-dependent calculation and by assuming an exponential decay law for the resonances formed, we have computed lifetimes of selective-adsorption resonances (SAR s) in the elastic scattering of He atoms from the Cu(110) and Cu(117) surfaces. In previous works, where SAR's were studied within the time-independent close-coupling method, we found that in addition to the energy width obtained by analyzing plots of diffraction intensities versus the energy of the incident beam, another internal energy width (with a very different numerical value) can be defined. Here we show that it is this internal width that can be directly related to the lifetime of the resonance. Also, we have performed a simulation of the half collision or "selective-desorption" process. This approach is shown to yield accurate values for lifetimes of SAR's.