A mass spectrometer for high‐pressure ion–molecule reaction studies was constructed using a pulsed 4‐keV electron beam and pulsed “gate‐open” mass‐spectrometer detection. The ions drift out of the field‐free ion source by diffusion and mass flow. Pressures up to 10 torr can be used and the ion reaction times can be as long as several hundred microseconds. The system is specially suited for study of reactions with very small rate constants, long reaction sequences, and reactions dependent on third‐body deactivation. Also when reverse reactions are operative the establishment of the equilibrium can be directly followed. The thermal rate constants for the reactions of Kr+ with CH4, and CH4+ and CH3+ with CH4, were measured. The reaction of O2+ with O2 to form O4+ is found to be third order, proceeding with a rate constant K = 2.8 × 10−30cm6molecules−2·sec−1 at 298°K. The activation energy for the reaction is negative and equal to 1–2 kcal/mole. The equilibrium constants for the reaction O2+ + 202⇄O4 + +O2 were determined over the temperature range 295°–350°K. A Vant Hoff plot of the equilibrium constant gives D(O2+–O2≃10 kcal/mole. The equilibrium constants and bond dissociation energy are in very good agreement with earlier results by Yang and Conway. Interesting comparisons with the N4+ formation in nitrogen can be made.

1.
P.
Kebarle
and
E. W.
Godbole
,
J. Chem. Phys.
39
,
1131
(
1963
).
2.
P.
Kebarle
,
R. M.
Haynes
, and
S.
Searles
,
Advan. Chem.
58
,
210
(
1966
).
3.
R. M.
Haynes
and
P.
Kebarle
,
J. Chem. Phys.
45
,
3899
(
1966
).
4.
P.
Kebarle
and
R. M.
Haynes
,
J. Chem. Phys.
47
,
1676
(
1967
).
5.
P.
Kebarle
,
R. M.
Haynes
, and
S. K.
Searles
,
J. Chem. Phys.
47
,
1684
(
1967
).
6.
V. L.
Talroze
and
E. L.
Frankevich
,
Zh. Fiz. Khim.
34
,
2709
(
1960
).
7.
(a)
T. W.
Shannon
,
F.
Meyer
, and
A. G.
Harrison
,
Can. J. Chem.
43
,
159
(
1965
).
(b)
A. G.
Harrison
,
J. J.
Myher
, and
J. C. J.
Thynne
,
Advan. Chem.
58
,
150
(
1966
).
8.
K. R.
Ryan
and
J. H.
Futrell
,
J. Chem. Phys.
42
,
824
(
1965
).
9.
H.
von Koch
,
Ark. Fysik
28
,
529
(
1965
).
V.
Cermàk
and
Z.
Herman
,
Nucleonics
9
,
106
(
1961
).
10.
F. H.
Field
and
M. S. B.
Munson
,
J. Am. Chem. Soc.
87
,
3289
(
1965
).
11.
A normalization to the total ion current is also practiced in conventional ion molecule reaction studies using continuous electron irradiation.12 In that case one needs to correct for the decrease of mass spectrometer sensitivity which occurs at higher pressures.
12.
S.
Wexler
and
R.
Marshall
,
J. Am. Chem. Soc.
86
,
781
(
1964
).
13.
Jae‐Hyun
Yang
and
D. C.
Conway
,
J. Chem. Phys.
40
,
1729
(
1964
).
14.
D. C.
Conway
and
Jae‐Hyun
Yang
,
J. Chem. Phys.
43
,
2900
(
1965
).
15.
R. N.
Varney
,
J. Chem. Phys.
31
,
1314
(
1959
).
16.
M.
Saporoschenko
,
Phys. Rev.
139
,
351
(
1965
).
17.
W. L.
Fite
,
J. A.
Rutherford
,
W. R.
Snow
, and
V. A. J.
van Lint
,
Discussions Faraday Soc.
33
,
264
(
1962
).
18.
Peter
Warneck
,
J. Chem. Phys.
46
,
502
(
1967
).
19.
F. C. Fehsenfeld, D. B. Bunkin, and D. K. Bohme, Communication at Sixteenth Conference on Mass Spectrometry and Allied Topics, Pittsburgh, Pa., 1968.
20.
H. B.
Palmer
and
D. F.
Hornig
,
J. Chem. Phys.
26
,
98
(
1957
).
21.
G.
Porter
,
Discussions Faraday Soc.
33
,
198
(
1962
).
22.
R. H. Fowler and E. A. Guggenheim, Statistical Thermodynamics (Cambridge University Press, Cambridge, England, 1939), p. 497.
23.
D. P. Stevenson, in Mass Spectrometry, C. A. McDowell, Ed. (McGraw‐Hill Book Co., New York, 1963).
24.
Varney15 obtained 0.5 eV for ΔH5a. The value of −ΔH5a should be close to D(N2+N2), a lower limit for which is set by the difference between the appearance potential of N4+ produced by the Hombeck‐Molnar process: N2*+N2 = N4++e, and the ionization potential of N2. The appearance potentials of
R. K.
Asundi
,
G. J.
Shulz
, and
P. J.
Chantry
,
J. Chem. Phys.
47
,
1584
(
1967
), lead to D(N2+N2)⩾0.6 eV.
This content is only available via PDF.
You do not currently have access to this content.