Laser-induced photo-desorption in the Na/Cu(1 1 1) system

Desorption in the Na/Cu(1 1 1) system induced by an electronic excitation is studied using a quantal approach. The system is excited by a laser pulse in the fs range to the Na∗ state corresponding to the transient capture of an electron by the alkali adsorbate. The present quantal approach describes on an equal footing the laser-induced vibrational excitation of the adsorbate in the adsorption well and the photo-desorption process. It confirms earlier results using a semi-classical input. It also allows a discussion of the photo-desorption probability with the photon energy: the maximum of the desorption probability per absorbed photon occurs off-resonance in the high-energy wing of the electronic transition. This feature is related to the dynamics of the laser-induced process.