The time-resolved LMR method as used to measure elementary reaction rates of CI atoms and SiH3 radicals in pulse photolysis of S2Cl2 in the presence of SiH4

Lev Krasnoperov, E. N. Chesnokov, V. N. Panfilov

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Abstract

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.

Original languageEnglish (US)
Pages (from-to)297-305
Number of pages9
JournalChemical Physics
Volume89
Issue number2
DOIs
StatePublished - Sep 15 1984
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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