Electron attachment and detachment coefficients are reported for pure oxygen from analyses of the current waveforms observed in drift‐tube experiments. The results are consistent with the identification of the negative ion as O2 with an electron affinity of 0.43±0.02 eV. The two‐body collisional detachment coefficient for O2 in thermal equilibrium with the gas increases from 9×10−17 cm3/sec at 375°K to 1.4×10−14 cm3/sec at 575°K. The three‐body attachment coefficient for thermal electrons increases from 2.0±0.2×10−30 cm6/sec at 300°K to 2.8±0.5×10−30 cm6/sec at 530°K. The O2 ions are found to survive at least 3×108 elastic collisions without de‐excitation and so are believed to be in their lowest vibrational state. At low oxygen densities the current of detached electrons is separated from the negative‐ion current by applying a high‐frequency voltage to the control grid. At high oxygen densities the electrons and negative ions cross the tube in a narrow pulse at a drift velocity determined by the equilibrium concentrations of electrons and ions.

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2.
Short discussions of this work have appeared previously.
A. V.
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and
J. L.
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,
Phys. Rev. Letters
6
,
111
(
1961
);
Symp. Combust. 10th Cambridge, England, 1964, 569 (1965).
See also
J. L.
Pack
and
A. V.
Phelps
,
Bull. Am. Phys. Soc.
6
,
387
(
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J. L.
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and
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7
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(
1962
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Bull. Am. Phys. Soc.
3.
J. L.
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Phelps
,
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121
,
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(
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4.
L. B. Loeb, Basic Processes in Gaseous Electronics (University of California Press, Berkeley, California, 1955), Chap. 5.
5.
R. E.
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43
,
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(
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A. J.
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29
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49
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429
(
1959
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J. Opt. Soc. Am.
7.
This design is an improvement of that described by
D.
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C. G.
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A. O.
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22
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9.
H. B. Dwight, Tables of Integrals and Other Mathematical Data (The MacMillan Company, New York, 1947), p. 181.
10.
Examples of detailed fitting of theoretical and experimental waveforms are given in Ref. 8 and by
D.
Edelson
and
K. B.
McAfee
,Jr.
,
Rev. Sci. Instr.
35
,
187
(
1964
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and by
E. C.
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(
1965
).
11.
A simplified derivation of Eqs. (8) and (14) can be carried out by considering times which are long enough so that the electron density is independent of time but short enough so that the negative‐ion destruction is small and so that the ions have not moved. The current density of detached electrons is then the detachment frequency times the integral of the product of the negative‐ion density times the probability that a detached electron will reach the collector without attaching to the oxygen.
12.
One reason for a higher electron‐drift velocity than that given in Appendix I under the conditions of the high‐pressure experiments is that at an oxygen density of 1019cm−2 the frequency of electron attachment collisions is comparable with the frequency of energy‐loss collisions due to rotational excitation. See
M. H.
Mentzoni
and
R. V.
Narasinga Rao
,
Phys. Rev. Letters
14
,
779
(
1965
). Under such conditions the energy dependence of the electron‐energy distribution could be perturbed significantly from that for lower oxygen densities. One indication that this effect is small is the good fit of Eq. (16) to the experimental data such as shown in Fig. 7.
13.
As is shown by experiment in Part II of this series of articles, this result disagrees with the experimental results of
C. F.
Smith
and
D. C.
Conway
,
Rev. Sci. Instr.
33
,
726
(
1962
)
and the analysis of
D. C.
Conway
,
J. Chem. Phys.
36
,
2549
(
1962
). We do not find any evidence for terms independent of the O2 density or proportional to the square of the CO2 density. We therefore do not accept the value of the mean lifetime for O2 obtained by Conway but instead prefer the limits set by CPB.
14.
R. W.
Warren
and
J. H.
Parker
, Jr.
,
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J. L.
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V. A. J.
van Lint
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E. G.
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5
,
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See also General Atomic Division of General Dynamics Corporation, San Diego, California, Report GACD‐2461 (1961) (unpublished).
17.
G. J.
Schulz
,
Bull. Am. Phys. Soc.
6
,
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18.
Mass spectrometric studies of the negative ions formed in O2 at oxygen densities between 2×1016 and 1017cm−3 have recently been carried out by J. L. Moruzzi and A. V. Phelps (unpublished). These results show that the negative ion formed at E/N<3×β0−17Vcm2 in the three‐body attachment process is O2.
19.
G. Herzberg, Molecular Spectra and Molecular Structure (D. Van Nostrand Company, Inc., New York, 1945), Chap. 5.
20.
R. E. Meyerott, R. K. M. Landshoff, and J. Magee, Report LMSD‐48361, Lockheed Aircraft Corporation, Sunnyvale, California, December 1951.
21.
In Ref. 13, Conway derives rotational and Vibrational constants for O2 which are slightly different from those of O2. The difference in rotational constants result in a 10% decrease in the ratio of partition functions on the right‐hand side of Eqs. (14) and (15). This corresponds to a 10% decrease in the theoretical intercept of Fig. 13 and has a negligible effect on the electron affinity derived from the experimental data.
22.
R. S.
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Phys. Rev.
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K. Takayanagi, Report No. 17, Joint Institute for Laboratory Astrophysics, University of Colorado, Boulder, Colorado, August 1964 (unpublished).
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J. G.
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34
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(
1961
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R.
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F. A.
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W.
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Proc. Phys. Soc. (London)
81
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D. S.
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H. O.
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28.
These experiments are discussed in detail in Ref. 4.
29.
H.
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(
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).
30.
Recent papers on this subject are:
G. C.
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69
,
3296
(
1964
);
G. C.
Reid
,
Rev. Geophys.
2
,
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(
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L. M.
Branscomb
,
Ann. Geophys.
20
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(
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L. R.
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J. B.
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13
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(
1965
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J. S.
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42
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1921
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32.
H. L.
Brose
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Phil. Mag.
50
,
536
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1925
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33.
R. H. Healey and C. B. Kirkpatrick, as given in R. H. Healey and J. W. Reed, The Behavior of Slow Electrons in Gases (Amalgamated Radio, Sydney, Australia, 1941), p. 94.
34.
R. A.
Nielsen
and
N. E.
Bradbury
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Phys. Rev.
51
,
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1937
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A.
Doehring
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7a
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36.
J. A.
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18
,
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37.
R. D. Hake, Jr. and A. V. Phelps (unpublished).
38.
F. C.
Fehsenfeld
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J. Chem. Phys.
39
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1963
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39.
M. H.
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69D
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213
(
1965
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40.
J. J.
Lowke
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G. S.
Hurst
and
T. E.
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42.
A. V.
Phelps
,
Natl. Bur. Std.
Tech. Note No. 211,
5
, April (
1964
).
43.
It is of interest to note that in the case of 7.8% O2, the rate of attachment and detachment collisions involving N2 is approximately equal to the rate of collisions involving only O2.
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