FEL induced dynamics of small molecules on surfaces: N2O on NaCl(1 0 0)

The infrared laser-induced desorption of N2O condensed on the single crystal surface of NaCl(1 0 0) is studied. In investigations of the desorption process of molecules from surfaces as well as of the dynamics of vibrationally excited adsorbate systems, a selective excitation of specific molecular vibrations is desirable. The Free Electron Laser for Infrared eXperiments “FELIX” is providing rapidly tunable infrared radiation that is well suited for this kind of investigations. A comparison of the wavelength dependent desorption yield to the linear absorption spectrum shows that desorption of intact, neutral molecules occurs when FELIX is resonant with an infrared active mode of the molecules. An analysis of the time-of-flight spectra as well as the dependence of the desorption yield on the layer thickness, laser fluence and substrate temperature point towards a resonant heating mechanism. First measurements on the dynamics of the vibrationally excited adsorbate using pump–probe spectroscopy are presented.