Gaseous Electronics

48

BROMOTRICHLORO-METHANE

CONTENTS

48.1 Attachment Rates

48.2 Attachment Cross Sections

References

 

Bromotrichloromethane (CBrCl₃) is a polar, electron-attaching gas that has 92 electrons. The ionization potential is 10.6 eV.

48.1 ATTACHMENT RATES

Attachment occurs through the formation of Br⁻ and Cl⁻ ions according to reactions (Spanel et al., 1997)

$${\text{CCl}}_3\text{Br}+\text{e}\to {\text{CCl}}_3+{\text{Br}}^{-}+0.4\text{eV}$$ (48.1)

$${\text{CCl}}_3\text{Br}+\text{e}\to {\text{CCl}}_2{\text{Br+Cl}}^{-}+0.2\text{eV}$$ (48.2)

At 300 K the abundance of Cl⁻ ion is about 20% of the total (Cl⁻ + Br⁻) increasing to 80% at 540 K. The fraction of Cl⁻ ions increases with increasing temperature till the ratio becomes Cl⁻:Br⁻ = 3:1 (Spanel et al., 1997).

The attachment rate constants are shown in Table 48.1. Figure 48.1 shows the variation of attachment ...