Low Energy Electron Attachment by Some Chlorosilanes

In this paper, the rate coefficients (k) and activation energies (E-a) for SiCl4, SiHCl3, and Si(CH3)(2)(CH2Cl)Cl molecules in the gas phase were measured using the pulsed Townsend technique. The experiment was performed in the temperature range of 298-378 K, and carbon dioxide was used as a buffer gas. The obtained k depended on temperature in accordance with the Arrhenius equation. From the fit to the experimental data points with function described by the Arrhenius equation, the activation energies (E-a) were determined. The obtained k values at 298 K are equal to (5.18 +/- 0.22) x 10(-10) cm(3)center dot s(-1), (3.98 +/- 1.8) x 10(-9) cm(3)center dot s(-1) and (8.46 +/- 0.23) x 10(-11) cm(3)center dot s(-1) and E-a values were equal to 0.25 +/- 0.01 eV, 0.20 +/- 0.01 eV, and 0.27 +/- 0.01 eV for SiHCl3, SiCl4, and Si(CH3)(2)(CH2Cl)Cl, respectively. The linear relation between rate coefficients and activation energies for chlorosilanes was demonstrated. The DFT/B3LYP level coupled with the 6-31G(d) basis sets method was used for calculations of the geometry change associated with negative ion formation for simple chlorosilanes. The relationship between these changes and the polarizability of the attaching center (alpha(centre)) was found. Additionally, the calculated adiabatic electron affinities (AEA) are related to the alpha(centre).