Photoelectron spectra are reported for the CH2(X̃ 3B1)+e←CH2 (X̃ 2B1) and CH2(ã 1A1)+e←CH2 (X̃ 2B1) transitions of the methylene and perdeuterated methylene anions, using a new flowing afterglow photoelectron spectrometer with improved energy resolution (11 meV). Rotational relaxation of the ions to ∼300 K and partial vibrational relaxation to <1000 K in the flowing afterglow negative ion source reveal richly structured photoelectron spectra. Detailed rotational band contour analyses yield an electron affinity of 0.652±0.006 eV and a singlet–triplet splitting of 9.00±0.09 kcal/mol for CH2. (See also the following paper by Bunker and Sears.) For CD2, results give an electron affinity of 0.645±0.006 eV and a singlet–triplet splitting of 8.98±0.09 kcal/mol. Deuterium shifts suggest a zero point vibrational contribution of 0.27±0.40 kcal/mol to the observed singlet–triplet splitting, implying a Te value of 8.7±0.5 kcal/mol. Vibrational and partially resolved rotational structure is observed up to ∼9000 cm1 above the zero point vibrational level of the 3B1 states, revealing a previously unexplored region of the quasilinear potential surface of triplet methylene. Approximately 20 new vibration‐rotation energy levels for CH2 and CD2 are measured to a precision of ∼30 cm1 in the v2=2–7 region (bent molecule numbering). Bending vibrational frequencies in the methylene anions are determined to be 1230±30 cm1 for CH and 940±30 cm1 for CD2, and the ion equilibrium geometries are bracketed. The measured electron affinity also provides values for the bond strength and heat of formation of CH2, and the gas phase acidity of CH3. A detailed description of the new flowing afterglow photoelectron spectrometer is given.

1.
G.
Herzberg
and
J.
Shoosmith
,
Nature
183
,
1801
(
1959
).
2.
P. P. Gaspar and G. S. Hammond, in Carbenes, edited by R. A. Moss and M. Jones, Jr. (Wiley‐Interscience, New York, 1975), Vol. 2, pp. 207–362.
3.
W. T.
Borden
and
E. R.
Davidson
,
Annu. Rev. Phys. Chem.
30
,
125
(
1979
).
4.
E. R. Davidson, in Diradicals, edited by W. T. Borden (Wiley‐Interscience, New York, 1982), pp. 73–105.
5.
I.
Shavitt
,
Tetrahedron
41
,
1531
(
1985
).
6.
P. R. Bunker, in Comparison of Ab Initio Quantum Chemistry with Expert' ment, edited by R. J. Bartlett (Reidel, Dordrecht, 1985).
7.
P. F.
Zittel
,
G. B.
Ellison
,
S. V.
ONeil
,
E.
Herbst
,
W. C.
Lineberger
, and
W. P.
Reinhardt
,
J. Am. Chem. Soc.
98
,
3731
(
1976
).
8.
P. C.
Engelking
,
R. R.
Corderman
,
J. J.
Wendoloski
,
G. B.
Ellison
,
S. V.
ONeil
, and
W. C.
Lineberger
,
J. Chem. Phys.
74
,
5460
(
1981
).
9.
P. M.
Kelley
and
W. L.
Hase
,
Chem. Phys. Lett.
35
,
57
(
1975
).
10.
J. W.
Simons
and
R.
Curry
,
Chem. Phys. Lett.
38
,
171
(
1976
).
11.
F.
Lahmani
,
J. Phys. Chem.
80
,
2623
(
1976
).
12.
H. M.
Frey
and
G. J.
Kennedy
,
J. Chem. Soc. Faraday Trans. 1
73
,
164
(
1977
).
13.
R. K.
Lengel
and
R. N.
Zare
,
J. Am. Chem. Soc.
100
,
7495
(
1978
).
14.
D.
Feldmann
,
K.
Meier
,
H.
Zacharias
, and
K. H.
Welge
,
Chem. Phys. Lett.
59
,
171
(
1978
).
15.
C. C.
Hayden
,
D. M.
Neumark
,
K.
Shobatake
,
R. K.
Sparks
, and
Y. T.
Lee
,
J. Chem. Phys.
76
,
3607
(
1982
).
16.
A. R. W.
McKellar
,
P. R.
Bunker
,
T. J.
Sears
,
K. M.
Evenson
,
R. J.
Saykally
, and
S. R.
Langhoff
,
J. Chem. Phys.
79
,
5251
(
1983
).
17.
B. O.
Roos
and
P. M.
Siegbahn
,
J. Am. Chem. Soc.
99
,
7716
(
1977
).
18.
(a)
L. B.
Harding
and
W. A.
Goddard
III
,
J. Chem. Phys.
67
,
1777
(
1977
);
(b)
L. B.
Harding
and
W. A.
Goddard
III
,
Chem. Phys. Lett.
55
,
217
(
1978
).
19.
C. W.
Bauschlicher
and
I.
Shavitt
,
J. Am. Chem. Soc.
100
,
739
(
1978
).
20.
S. K.
Shih
,
S. D.
Peyerimhoff
,
R. J.
Buenker
, and
M.
Peric
,
Chem. Phys. Lett.
55
,
206
(
1978
).
21.
P.
Saxe
,
H. F.
Schaefer
III
, and
N. C.
Handy
,
J. Phys. Chem.
85
,
745
(
1981
).
22.
H.‐J.
Werner
and
R.‐A.
Reinsch
,
J. Chem. Phys.
76
,
3144
(
1982
).
23.
S. J.
Cole
,
G. D.
Purvis
III
, and
R. J.
Bartlett
,
Chem. Phys. Lett.
113
,
271
(
1985
).
24.
P. J.
Reynolds
,
M.
Dupuis
, and
W. A.
Lester
, Jr.
,
J. Chem. Phys.
82
,
1983
(
1985
).
25.
T. J.
Sears
and
P. R.
Bunker
,
J. Chem. Phys.
79
,
5265
(
1983
).
26.
W. A.
Goddard
III
,
Science
227
,
916
(
1985
).
27.
D. G.
Leopold
,
K. K.
Murray
, and
W. C.
Lineberger
,
J. Chem. Phys.
81
,
1048
(
1984
).
28.
P. R.
Bunker
and
T. J.
Sears
,
J. Chem. Phys.
83
,
4866
(
1985
).
29.
W. A.
Lathan
,
W. J.
Hehre
,
L. A.
Curtiss
, and
J. A.
Pople
,
J. Am. Chem. Soc.
93
,
6377
(
1971
).
30.
J. H.
Meadows
and
H. F.
Schaefer
III
,
J. Am. Chem. Soc.
98
,
4383
(
1976
).
31.
P. J.
Hay
,
W. J.
Hunt
, and
W. A.
Goddard
,
J. Am. Chem. Soc.
94
,
8293
(
1972
).
32.
V.
Staemmler
,
Theor. Chim. Acta
35
,
309
(
1974
).
33.
J. F.
Harrison
and
L. C.
Allen
,
J. Am. Chem. Soc.
91
,
807
(
1969
).
34.
S. V.
ONeil
,
H. F.
Schaefer
III
, and
C. F.
Bender
,
J. Chem. Phys.
55
,
162
(
1971
).
35.
M. L.
Halberstadt
and
J. R.
McNesby
,
J. Am. Chem. Soc.
89
,
3417
(
1967
).
36.
R. W.
Carr
,
T. W.
Eder
, and
M. G.
Topor
,
J. Chem. Phys.
53
,
4716
(
1970
).
37.
T. J.
Sears
,
P. R.
Bunker
, and
A. R. W.
McKellar
,
J. Chem. Phys.
77
,
5363
(
1982
).
38.
K. E.
McCulloh
and
V. H.
Dibeler
,
J. Chem. Phys.
64
,
4445
(
1976
).
39.
(a)
W. A.
Chupka
,
J. Chem. Phys.
48
,
2337
(
1968
);
(b)
W. A.
Chupka
and
C.
Lifshitz
,
J. Chem. Phys.
48
,
1109
(
1968
).,
J. Chem. Phys.
40.
C. F.
Bender
and
H. F.
Schaefer
III
,
J. Am. Chem. Soc.
92
,
4984
(
1970
).
41.
R. A.
Bernheim
,
H. W.
Bernard
,
P. S.
Wang
,
L. S.
Wood
, and
P. S.
Skell
,
J. Chem. Phys.
53
,
1280
(
1970
).
42.
E.
Wasserman
,
V. J.
Kuck
,
R. S.
Hutton
, and
W. A.
Yager
,
J. Am. Chem. Soc.
92
,
7491
(
1970
).
43.
G.
Herzberg
and
J. W. C.
Johns
,
J. Chem. Phys.
54
,
2276
(
1971
).
44.
P. R.
Bunker
and
P.
Jensen
,
J. Chem. Phys.
79
,
1224
(
1983
).
45.
G.
Herzberg
and
J. W. C.
Johns
,
Proc. R. Soc. London Ser. A
295
,
107
(
1966
).
46.
A. R. W.
McKellar
,
C.
Yamada
, and
E.
Hirota
,
J. Chem. Phys.
79
,
1220
(
1983
).
47.
T. J.
Sears
,
P. R.
Bunker
,
A. R. W.
McKellar
,
K. M.
Evenson
,
D. A.
Jennings
, and
J. M.
Brown
,
J. Chem. Phys.
77
,
5348
(
1982
).
48.
J. W. C.
Johns
,
Can. J. Phys.
45
,
2639
(
1967
).
49.
S.
Carter
and
N. C.
Handy
,
J. Mol. Spectrosc.
95
,
9
(
1983
).
50.
P. R.
Bunker
,
Annu. Rev. Phys. Chem.
34
,
59
(
1983
).
51.
B.
Brehm
,
M. A.
Gusinow
, and
J. L.
Hall
,
Phys. Rev. Lett.
19
,
737
(
1967
).
52.
M. W.
Siegel
,
R. J.
Celotta
,
J. L.
Hall
,
J.
Levine
, and
R. A.
Bennett
,
Phys. Rev. A
6
,
607
(
1972
).
53.
C. S. Feigerle, A. E. S. Miller, D. Spence, S. M. Bumett, and W. C. Lineberger, Rev. Sci. Instrum. (to be published).
54.
C. S. Feigerle, Ph.D. thesis, University of Colorado, 1983.
55.
J.
Cooper
and
R. N.
Zare
,
J. Chem. Phys.
48
,
942
(
1968
).
56.
E. E.
Ferguson
,
F. C.
Fehsenfeld
, and
A. L.
Schmeltekopf
,
Adv. At. Mol. Phys.
5
,
1
(
1969
).
57.
G. I.
Mackay
,
G. D.
Vlachos
,
D. K.
Bohme
, and
H. I.
Schiff
,
Int. J. Mass Spectrom. Ion Phys.
36
,
259
(
1980
).
58.
D.
Smith
and
N. G.
Adams
,
J. Phys. D
13
,
1267
(
1980
).
59.
C. H.
Depuy
and
V. M.
Bierbaum
,
Acc. Chem. Res.
14
,
146
(
1981
).
60.
D. L.
Albritton
,
At. Data Nucl. Data Tables
22
,
1
(
1978
).
61.
R. S.
Gao
,
P. S.
Gibner
,
J. H.
Newman
,
K. A.
Smith
, and
R. F.
Stebbings
,
Rev. Sci. Instrum.
55
,
1756
(
1984
).
62.
V. M. Bierbaum and C. H. Depuy (private communication).
63.
D. M. Neumark, K. R. Lykke, T. Andersen, and W. C. Lineberger, Phys. Rev. A (to be published).
64.
M. N. R.
Ashfold
,
M. A.
Fullstone
,
G.
Hancock
, and
G.
Duxbury
,
Mol. Phys.
45
,
887
(
1982
).
65.
P. C.
Cross
,
R. M.
Hainer
, and
G. W.
King
,
J. Chem. Phys.
12
,
210
(
1944
).
66.
P. R.
Bunker
,
T. J.
Sears
,
A. R. W.
McKellar
,
K. M.
Evenson
, and
F. J.
Lovas
,
J. Chem. Phys.
79
,
1211
(
1983
).
67.
We are grateful to P. R. Bunker and T. J. Sears for providing us with the unpublished parts of the calculations reported in the following paper.
68.
(a)
R. N.
Dixon
,
Trans. Faraday Soc.
60
,
1363
(
1964
);
(b)
J. M.
Berthou
,
B.
Pascat
,
H.
Guenebaut
, and
D. A.
Ramsay
,
Can. J. Phys.
50
,
2265
(
1972
).
69.
(a) V. M. Bierbaum, G. B. Ellison, and S. R. Leone, in Gas Phase Ion Chemistry, edited by M. T. Bowers (Academic, New York, 1984), Vol. III, pp. 1–39;
(b)
H.
Böhringer
,
M.
Durup‐Ferguson
,
D. W.
Fahey
,
F. C.
Fehsenfeld
, and
E. E.
Ferguson
,
J. Chem. Phys.
79
,
4201
(
1983
).
70.
G. M.
McClelland
,
K. L.
Saenger
,
J. J.
Valentini
, and
D. R.
Herschbach
,
J. Phys. Chem.
83
,
947
(
1979
).
71.
A. J.
Merer
and
D. N.
Travis
,
Can. J. Phys.
44
,
525
(
1966
).
72.
Y.
Osamura
,
Y.
Yamaguchi
, and
H. F.
Schaefer
III
,
J. Chem. Phys.
75
,
2919
(
1981
).
73.
The stretching vibrations in the A11 state of CH2 are 2805.9 cm−1 for ν1 and 2864.5 cm−1 for ν3 [
H.
Petek
,
D. J.
Nesbitt
,
P. R.
Ogilby
, and
C. B.
Moore
,
J. Phys. Chem.
87
,
5367
(
1983
)].
74.
G. Herzberg, Molecular Spectra and Molecular Structure (van Nostrand, Princeton, 1945), Vol. II, p. 228–238.
75.
D.
Feldmann
,
K.
Meier
,
R.
Schmiedl
, and
K. H.
Welge
,
Chem. Phys. Lett.
60
,
30
(
1978
).
76.
D.
Feldmann
,
Chem. Phys. Lett.
47
,
338
(
1977
).
77.
A.
Kasdan
,
E.
Herbst
, and
W. C.
Lineberger
,
Chem. Phys. Lett.
31
,
78
(
1975
).
78.
D.
Feller
,
L. E.
McMurchie
,
W. T.
Borden
, and
E. R.
Davidson
,
J. Chem. Phys.
77
,
6134
(
1982
).
79.
As was pointed out in Ref. 48, the term “barrier” is not really correct in this case since the potential has a circular minimum; the molecule can go “between minima” by means of a rotation.
80.
W. R.
Thorson
and
I.
Nakagawa
,
J. Chem. Phys.
33
,
994
(
1960
).
81.
JANAF Thermochemical Tables, edited by D. R. Stull and H. Prophet, Natl. Stand. Ref. Data Ser. Natl. Bur. Stand. NSRDS‐NBS 37 (U.S. GPO, Washington, DC, 1971).
82.
P.
Jensen
,
P. R.
Bunker
, and
A. R.
Hoy
,
J. Chem. Phys.
77
,
5370
(
1982
).
83.
J. E. Bartmess and R. T. McIver, Jr., in Gas Phase Ion Chemistry, edited by M. T. Bowers (Academic, New York, 1979), Vol. 2, pp. 87–121.
84.
G. B.
Ellison
,
P. C.
Engelking
, and
W. C.
Lineberger
,
J. Am. Chem. Soc.
100
,
2556
(
1978
).
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