The rotational spectrum of the molecular negative ion CN has been detected in the laboratory at high resolution. The four lowest transitions were observed in a low pressure glow discharge through C2N2 and N2. Conclusive evidence for the identification was provided by well-resolved nitrogen quadrupole hyperfine structure in the lowest rotational transition, and a measurable Doppler shift owing to ion drift in the positive column of the discharge. Three spectroscopic constants (B, D, and eQq) reproduce the observed spectrum to within one part in 107 or better, allowing the entire rotational spectrum to be calculated well into the far IR to within 1kms1 in equivalent radial velocity. CN is an excellent candidate for astronomical detection, because the CN radical is observed in many galactic molecular sources, the electron binding energy of CN is large, and calculations indicate CN should be detectable in IRC+10216—the carbon star where C6H has recently been observed. The fairly high concentration of CN in the discharge implies that other molecular anions containing the nitrile group may be within reach.

1.
J. C.
Rienstra-Kiracofe
,
G. S.
Tschumper
,
H. F.
Schaefer
 III
,
S.
Nandi
, and
G. B.
Ellison
,
Chem. Rev. (Washington, D.C.)
102
,
231
(
2002
).
2.
S. E.
Bradforth
,
E. H.
Kim
,
D. W.
Arnold
, and
D. M.
Neumark
,
J. Chem. Phys.
98
,
800
(
1993
).
3.
M. C.
McCarthy
,
C. A.
Gottlieb
,
H.
Gupta
, and
P.
Thaddeus
,
Astrophys. J. Lett.
652
,
L141
(
2006
).
4.
S.
Brünken
,
C. A.
Gottlieb
,
H.
Gupta
,
M. C.
McCarthy
, and
P.
Thaddeus
,
Astron. Astrophys. Lett.
464
,
L33
(
2007
).
5.
H.
Gupta
,
S.
Brünken
,
F.
Tamassia
,
C. A.
Gottlieb
,
M. C.
McCarthy
, and
P.
Thaddeus
,
Astrophys. J. Lett.
655
,
L57
(
2007
).
6.
A.
Kühn
,
H.-P.
Fenzlaff
, and
E.
Illenberger
,
Chem. Phys. Lett.
135
,
335
(
1987
).
7.
B and μ from
P.
Botschwina
,
S.
Seeger
,
M.
Mladenović
,
B.
Schulz
,
M.
Horn
,
S.
Schmatz
,
J.
Flügge
, and
R.
Oswald
,
Int. Rev. Phys. Chem.
14
,
169
(
1995
);
D and H from
P.
Botschwina
,
Chem. Phys. Lett.
114
,
58
(
1985
).
8.
T. J.
Lee
and
C. E.
Dateo
,
Spectrochim. Acta, Part A
55
,
739
(
1999
).
9.
Be from a CCSD(T)/aug-cc-pCV5Z calculation; α, D, and eQq calculated with an aug-cc-pCVQZ basis set [
H.
Gupta
(private communication)].
10.
D. D.
Skatrud
,
F. C.
De Lucia
,
G. A.
Blake
, and
K. V. L. N.
Sastry
,
J. Mol. Spectrosc.
99
,
35
(
1983
).
11.
F. J.
Lovas
,
J. Phys. Chem. Ref. Data
7
,
1445
(
1978
).
12.
A. E.
Douglas
and
P. M.
Routly
,
Astrophys. J.
119
,
303
(
1954
).
13.

At the same level of theory, eQq for CN (Ref. 20) is in excellent agreement with the measured value (Table II).

14.
S. K.
Stephenson
and
R. J.
Saykally
,
Chem. Rev. (Washington, D.C.)
105
,
3220
(
2005
).
15.
T. J.
Lee
and
C. E.
Dateo
,
J. Chem. Phys.
107
,
10373
(
1997
).
16.
K. A.
Peterson
and
R. C.
Woods
,
J. Chem. Phys.
87
,
4409
(
1987
).
17.
A.
von Engel
,
Ionized Gases
(
AIP
,
Woodbury, NY
,
1994
).
18.
W.
Sailer
,
A.
Pelc
,
P.
Limão-Vieira
,
N. J.
Mason
,
J.
Limtrakul
,
P.
Scheier
,
M.
Probst
, and
T. D.
Märk
,
Chem. Phys. Lett.
381
,
216
(
2003
).
19.
K.
Graupner
,
T. L.
Merrigan
,
T. A.
Field
,
T. G. A.
Youngs
, and
P. C.
Marr
,
New J. Phys.
8
,
117
(
2006
).
20.
R.
Polák
and
J.
Fišer
,
Spectrochim. Acta, Part A
58
,
2029
(
2002
).
21.
V. G.
Anicich
and
W. T.
Huntress
, Jr.
,
Astrophys. J., Suppl. Ser.
62
,
533
(
1986
).
22.
A.
Dalgarno
and
R. A.
McCray
,
Astrophys. J.
181
,
95
(
1973
).
23.
P. J.
Sarre
,
J. Chim. Phys. Phys.-Chim. Biol.
77
,
769
(
1980
).
24.
S.
Petrie
,
Mon. Not. R. Astron. Soc.
281
,
137
(
1996
).
25.
C.
Savage
,
A. J.
Apponi
, and
L. M.
Ziurys
,
Astrophys. J.
578
,
211
(
2002
).
26.
M.
Allen
and
G. R.
Knapp
,
Astrophys. J.
225
,
843
(
1978
).
27.
J.
Cernicharo
and
M.
Guélin
(private communication).
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