Abstract:
We report a comparative study of the impact of repetitively pulsed neodymium laser radiation of the first (λ1 = 1064 nm, τ1 = 12 ns) and second (λ2 = 532 nm, τ2 = 10 ns) harmonics on tableted microparticles of brown (2B), gas (G), and fat (Zh) coals. The concentration of synthesis gas molecules formed when microparticles of hard coals are exposed to laser pulses of the same energy density is higher in the case of the second-harmonic radiation. The concentration of synthesis gas molecules formed when microparticles of coals are exposed to first- and second-harmonic pulses of the same intensity is the same. A model is proposed to explain the nonlinear dependence of the synthesis gas yield on the intensity of laser pulses, based on the nonlinear generation of primary centers of thermochemical reactions formed during optical breakdown of coal samples and generation of laser-induced plasma. The spectral intensity of the laser-induced plasma glow when tableted samples of coal microparticles are irradiated by the second-harmonic laser pulses is higher than that during irradiation by the first-harmonic pulses, with radiation energy densities being the same.
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