The time-resolved laser magnetic resonance (LMR) method has been applied to kinetic measurements for the first time. An intracavity spectrometer based on a CO2 laser with resonant modulation of the magnetic field and with phase-sensitive detection of the signal has been used. Kinetic curves of generation and disappearance of CI atoms and SiH3 radicals were obtained in the pulse photolysis of a mixture of S2Cl2 + SiH4 under the fourth harmonic of a Nd laser (265 nm, 0.5 mJ, 12.5 Hz) at a total pressure of 520-980 Pa (he as diluent) and a temperature of 326 K. The reagent concentrations were: [S2Cl2 = (2.0-10.2)×1014 cm-3, [SiH4 = (2.4-17.4)×1013 cm-3. To remove the transition saturation, 5.3×1015 cm-3 CCl4 was introduced into the reactor. The fraction of dissociated S2Cl2 was 1‰ Rate constants of the reactions (I) Cl+S2Cl2 → products, (II) Cl+SiH4 → HCl+SiH3 and a preliminary rate constant of the reaction (III) SiH3 + S2Cl2 → products were obtained: k1 ≤ (4.3±1.2)×10-12 cm3/s, k2 = (2.3±0.5)×10-10 cm3/s, k3 = (2.4±0.5)×10-11 cm3/s. At a signal-to-noise ratio of 1:1, 1000 pulses and a 12 cm long detection zone the sensitivity to Cl atoms and to SiH3 radicals was 4×1010 cm-3 and = 1011 cm-3, respectively. The time resolution of the method was 4 μs. The method is shown to be promising for kinetic investigations and experiments on fast processes.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry