Simulations of the femtosecond laser-induced desorption of CO from Cu(100) at 0.5 ML coverage

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Simulations of the femtosecond laser-induced desorption of CO from Cu(100) at an initial temperature of 95K are reported, employing molecular dynamics with electronic frictions. Results are obtained for saturation (0.5 ML) CO coverage, which are compared with additional simulations in the zero coverage limit. In both cases, the desorption yield depends nonlinearly on laser fluence, with initial nonadiabatic energy flow occurring selectively from hot substrate electrons to the molecule-surface frustrated rotation. There is significant enhancement of the desorption yield at saturation relative to the zero coverage limit. This is due to conversion of momentum in the plane of the surface to normal momentum, by collisions between an energetic adsorbate and its neighbors, and energy pooling between molecules in the overlayer.