This study investigates the kinetics of thermal desorption from an excimer-laser-melted silicon surface, where chlorine diffusion into the bulk competes with desorption. A combination of experimental techniques—including Auger electron spectroscopy (AES), time-of-flight mass spectrometry (TOF), secondary-ion mass spectrometry (SIMS), and transient reflectivity—are used to analyze the desorption and diffusion processes. Numerical modeling is employed to describe nonequilibrium thermal diffusion, phase transition effects, segregation, and both first- and second-order desorption kinetics. The results show that activation desorption energies are lower for the liquid silicon phase compared to the solid phase, differing by approximately 0.5 eV. The segregation coefficient of chlorine at the liquid-solid interface is determined to be < 0.02, with a recrystallization speed of ~6 m/s. Desorption rates reach up to 1 ML/ns, efficiently depleting the silicon surface of Cl atoms through combined desorption and diffusion mechanisms. After only three laser pulses, Cl contamination levels are significantly reduced, exhibiting a logarithmic decrease over multiple pulses. These findings demonstrate the effectiveness of pulsed laser-induced surface melting for impurity removal and provide insights into surface modification dynamics under extreme thermal conditions.