Guided-ion beam cross section and product ion time-of-flight (TOF) measurements are presented for the O+(4S)+C2H2 reaction over the center-of-mass collision energy range of 0.05–18 eV. Despite a large number of exothermic channels, the total reaction cross section at low energies is more than two orders of magnitude smaller than the capture cross section. A common energy onset for charge-transfer, CH+, and COH+/HCO+ products is observed at 1.70±0.10 eV, above which the total cross section for these channels rapidly rises with energy, eventually exceeding 5 Å2. Above 4 eV, the C2H+ and CO+ products also become significant, and weaker channels producing C+,C2+, and CH2O+ are also identified. The C2H+ fragment is interpreted as being primarily a dissociative charge transfer (CT) channel at collision energies above ∼3.79 eV, while the threshold for forming CO+ can be associated with a CO++H+CH channel. The TOF measurements demonstrate that efficient C2H2+ Ã state formation occurs above ∼2.7 eV. The onset at 1.70±0.10 eV is attributed to a transition state associated with an excited quartet hypersurface.

1.
E.
Teloy
and
D.
Gerlich
,
Chem. Phys.
4
,
417
(
1974
).
2.
D. Gerlich, in State-Selected and State-to-State Ion Molecule Reaction Dynamics: Experiment, Part I. Adv. Chem. Phys. Vol. 82, edited by C. Y. Ng and M. Baer (Wiley, New York, 1992), p. 1.
3.
Y.
Chiu
,
H.
Fu
,
J.
Huang
, and
S. L.
Anderson
,
J. Chem. Phys.
102
,
1199
(
1995
).
4.
R. A.
Curtis
and
J. M.
Farrar
,
J. Chem. Phys.
90
,
862
(
1989
).
5.
J.
Qian
,
H.
Fu
, and
S. L.
Anderson
,
J. Phys. Chem.
101
,
6504
(
1997
).
6.
J.
Qian
,
R. J.
Green
, and
S. L.
Anderson
,
J. Chem. Phys.
108
,
7173
(
1998
).
7.
S. G.
Lias
,
J. E.
Bartmess
,
J. F.
Liebman
,
J. L.
Holmes
,
R. D.
Levin
, and
W. G.
Mallard
,
Gas-Phase Ion and Neutral Thermochimstry
,
J. Phys. Chem. Ref. Data
17,
Suppl 1 (
1988
).
8.
A. A. Radzig and B. M. Smirnov, Reference Data on Atoms, Molecules, and Ions (Springer-Verlag, Berlin, 1985).
9.
K. P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules (Van Nostrand Reinhold, New York, 1979).
10.
G. Herzberg, Molecular Spectra and Molecular Structure III. Electronic Spectra and Electronic Structure of Polyatomic Molecules (Van Nostrand Reinhold, New York, 1966).
11.
M. J.
Bastian
,
R. A.
Dressler
,
E.
Murad
,
S. T.
Arnold
, and
A. A.
Viggiano
,
J. Chem. Soc., Faraday Trans.
92
,
2659
(
1996
).
12.
R. A. Dressler and E. Murad, in Unimolecular and Bimolecular Ion-Molecule Reaction Dynamics, edited by C. Y. Ng, T. Baer, and I. Powis (Wiley, New York, 1994), p. 87.
13.
E.
Murad
,
J. Spacecr. Rockets
33
,
131
(
1996
).
14.
O. J.
Orient
,
A.
Chutjian
, and
K. E.
Martus
,
Phys. Rev. A
48
,
427
(
1993
).
15.
O. J.
Orient
,
A.
Chutjian
, and
E.
Murad
,
Phys. Rev. A
51
,
2094
(
1995
).
16.
M.
Mendillo
,
J.
Baumgartner
,
P. D.
Allen
,
J.
Foster
,
J.
Holt
,
G. R. A.
Ellis
,
A.
Klekociuk
, and
G.
Reber
,
Science
238
,
1260
(
1987
).
17.
R. A.
Dressler
,
R. H.
Salter
, and
E.
Murad
,
J. Chem. Phys.
99
,
1159
(
1993
).
18.
C. E.
Moore
,
Natl. Bur. Stand., Circ.
467,
Vol. I, p.
47
(
1949
).
19.
T. O.
Tiernan
and
B. M.
Hughes
,
J. Chem. Phys.
55
,
3419
(
1971
).
20.
J. A.
Appell
,
J.
Durup
, and
F.
Heitz
,
Adv. Mass Spectrom.
3
,
457
(
1969
).
21.
J. L.
Franklin
,
J. G.
Dillard
,
H. M.
Rosenstock
,
J. T.
Herron
,
K.
Draxl
, and
F. H.
Field
,
Ionization Potentials, Appearance Potentials, and Heats of Formation of Gaseous Positive Ions, Nat. Stand. Ref. Data Ser.
26
, (
1969
).
22.
K. M.
Ervin
and
P. B.
Armentrout
,
J. Chem. Phys.
83
,
166
(
1985
).
23.
Y. Ikezoe, S. Matsuoka, M. Takabe, and A. A. Viggiano, Gas Phase Ion-Molecule Reaction Rate Constants Through 1986 (Maruzen Co., Tokyo, 1987).
24.
P. J.
Derrick
and
I.
Szabo
,
Int. J. Mass Spectrom. Ion Phys.
7
,
55
(
1971
).
25.
G.
Gioumousis
and
D. P.
Stevenson
,
J. Chem. Phys.
29
,
294
(
1958
).
26.
M. J.
Bastian
,
R. A.
Dressler
,
D. J.
Levandier
,
E.
Murad
,
F.
Muntean
, and
P. B.
Armentrout
,
J. Chem. Phys.
106
,
9570
(
1997
).
27.
D.
Gerlich
,
J. Chem. Phys.
90
,
127
(
1989
).
28.
J. E.
Reutt
,
L. S.
Wang
,
J. E.
Pollard
,
D. J.
Trevor
,
Y. T.
Lee
, and
D. A.
Shirley
,
J. Chem. Phys.
84
,
3022
(
1986
).
29.
G. A.
Fisk
,
J. D.
McDonald
, and
D. R.
Herschbach
,
Discuss. Faraday Soc.
44
,
228
(
1967
).
30.
M. K.
Bullit
,
C. H.
Fisher
, and
J. L.
Kinsey
,
J. Chem. Phys.
60
,
478
(
1974
).
31.
D. M.
Sonnernfroh
,
R. A.
Curtis
, and
J. M.
Farrar
,
J. Chem. Phys.
83
,
3958
(
1985
).
32.
GAUSSIAN 94, Revision D.1, M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb,, T. K. J. R. Cheeseman, G. A. Petersson, J. A. Montgomery, K. Raghavachari, V. G. Z. M. A. Al-Laham, J. V. Ortiz, J. B. Foresman, J. Cioslowski,, A. N. B. B. Stefanov, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen,, J. L. A. M. W. Wong, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, D. J. D. J. S. Binkley, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez,, and J. A. Pople (Gaussian, Inc., Pittsburgh PA, 1995).
33.
A.
Luna
,
A. M.
Mebel
, and
K.
Morokuma
,
J. Chem. Phys.
105
,
3187
(
1996
).
34.
W. J.
Bouma
,
P. M. W.
Gill
, and
L.
Radom
,
Org. Mass Spectrom.
19
,
610
(
1984
).
35.
E. A. Gislason, G. Parlant, and M. Sizun, in State-Selected and State-to-State Ion-Molecule Reaction Dynamics, Part II, Adv. Chem. Phys., Vol. 82, edited by C. Y. Ng and M. Baer (Wiley, New York, 1992), p. 321.
36.
H. Nakamura, in State-Selected and State-to-State Ion-Molecule Reaction Dynamics, Part II Adv. Chem. Phys. Vol. 82, edited by C. Y. Ng and M. Baer (Wiley, New York, 1992), p. 243.
37.
J. D.
Burley
,
K. M.
Ervin
, and
P. B.
Armentrout
,
J. Chem. Phys.
86
,
1944
(
1986
).
38.
C.
Servais
and
R.
Locht
,
Chem. Phys. Lett.
236
,
96
(
1995
).
39.
C.
Cha
,
R.
Weinkauf
, and
U.
Boesl
,
J. Chem. Phys.
103
,
5224
(
1995
).
40.
P.
Rosmus
,
P.
Botschwina
, and
J. P.
Maier
,
Chem. Phys. Lett.
84
,
71
(
1981
).
41.
W. P.
Kraemer
and
W.
Koch
,
Chem. Phys. Lett.
212
,
631
(
1993
).
42.
G.
Chambaud
,
R.
Van den Boom
, and
P.
Rosmus
,
Chem. Phys. Lett.
247
,
79
(
1995
).
43.
T. C.
Hamilton
and
H. F.
Schaefer
, III
,
J. Phys. Chem.
93
,
7560
(
1989
).
44.
J.
Baker
,
Chem. Phys. Lett.
159
,
447
(
1989
).
45.
K.
Norwood
and
C. Y.
Ng
,
J. Chem. Phys.
91
,
2898
(
1989
).
This content is only available via PDF.
You do not currently have access to this content.