Decay kinetics of thermal emission of surface layers of carbon materials under pulsed laser excitation

For surface layers of carbon materials, under excitation by a Q-switched neodymium laser, the decay of laser-induced thermal emission is investigated both experimentally and theoretically. It is revealed that the decay curves can be fit with satisfactory accuracy by a sum of two exponential components with the decay times of the order of 10 and 100 ns. Under irradiation by a sequence of laser pulses, the observed transformations of the emission decay curves can be presented as redistribution of intensity of the above-mentioned two components. As a result of computer simulations, it is concluded that the emission decay time is determined by the ratio of the penetration depth of laser radiation and the thermal diffusion length. This fact opens a possibility for estimation of thermal diffusivity of an investigated material in a thin surface layer at high temperatures (thousands of Kelvins).