TIME-RESOLVED STUDY OF LASER-INDUCED THERMAL-DESORPTION

A Pump-probe experiment was performed to study the desorption of ammonia from a Re(0001), at nsec time scale, following a pulsed laser induced thermal desorption. Optical second harmonic generation (SHG) was utilized to monitor the decreasing ammonia coverage as a function of delay time between the pump and the probe laser pulses. It was found that coverage dependent desorption kinetic parameters, determined under equilibrium conditions, could reproduce very well the nsec time scale desorption event. Thermal heat diffusion model, was found to predict correctly the surface temperature, therefore also the directly monitored desorption rates. Desorption is thus employed for the first time as an indirect probe of transient surface temperature changes at nsec time scale.