Decomposition of liquid hexamethyldisiloxane induced by CO2 laser pulse heating of carbon particles Original Research Article

CO2 laser-induced decomposition of liquid hexamethyldisiloxane (Me3Si)2O with graphite sensitization has been studied. Suspended graphite is used for an effective heterogeneous sensitization due to very efficient absorption of CO2 laser radiation. In the experiments the laser line 10P16 (∼948 cm−1) coinciding with the absorption minimum of the aνSi–O band (1055 cm−1) of (Me3Si)2O is selected for irradiation. This choice allows to avoid radiation losses due to low (5.4×10−4 Torr−1 cm−1) vapor absorption and to ensure the maximum (>100 μm) penetration depth of the laser radiation into the liquid. The decomposition is a thermal process and can be denoted as pulsed laser thermolysis. A thermodynamic approach is proposed to evaluate the temperature of graphite particles and adjacent liquid layers resulting from the laser pulse heating. It is shown that for a 100 ns laser pulse at fluence of 1 J/cm2 adjacent liquid layers with a thickness of 0.2 μm can be heated to temperatures in the range of 400–800 °C. The high (>8 MPa) pressure inside the supercritical liquid layers favors the decomposition. The IR, mass analyses of irradiated liquid samples indicate the formation of linear polystructures as decomposition products.