Monatomic and Diatomic Ions in Oxygen

The reaction rate constants or the cross sections for charge-exchange reactions of the ions

O^{-}

O^{+}

O_{2}^{-}

, and

O_{2}^{+}

with

O_{2}

have been measured over a range of values of

\frac{E}{p_{0}}

. The rate constant for the

O^{-}

exchange rises from 2 ×

10^{- 13}

{cm}^{3}

/sec at

\frac{E}{p_{0}}

of 25 to 2.7 ×

10^{- 10}

{cm}^{3}

/sec at

\frac{E}{p_{0}}

of 300 V

{(cm Torr)}^{- 1}

. For

O^{+}

, the rate constant rises from 1.4 ×

10^{- 11}

{cm}^{3}

/sec at

\frac{E}{p_{0}}

of 20 to 2.9 ×

10^{- 11}

\frac{E}{p_{0}}

of 55. The resonant charge-exchange cross section for

O_{2}^{+}

O_{2}

is 40

Å^{2}

, and for

O_{2}^{-}

is 25

Å^{2}

at energies of about 0.2 eV. The drift velocities of

O^{-}

O_{2}^{-}

, and

O_{2}^{+}

in pure

O_{2}

are also presented. The mobilities for the molecular ions emerge as 2.4 ± 0.1

{cm}^{2}

{(V \sec)}^{- 1}

for ions of both signs when extrapolated to the limit of

\frac{E}{p_{0}}

of zero, and to

p_{0}

of 760 Torr. The values for

O^{-}

lie appreciably above those of Eiber and of Beaty. A method of producing relatively large currents of

O^{-}

has been found. It depends on using higher values of

\frac{E}{p_{0}}

then might be expected from attachment-coefficient data.

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