Dicarbon

Formula: C₂
Molecular weight: 24.0214
IUPAC Standard InChI: InChI=1S/C2/c1-2
IUPAC Standard InChIKey: LBVWYGNGGJURHQ-UHFFFAOYSA-N
CAS Registry Number: 12070-15-4
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript.
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Information on this page:
Other data available:
- Gas phase thermochemistry data
- Reaction thermochemistry data
Data at other public NIST sites:
- Gas Phase Kinetics Database
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Gas phase ion energetics data

Go To: Top, Ion clustering data, Constants of diatomic molecules, References, Notes

Data evaluated as indicated in comments:
L - Sharon G. Lias

Data compiled as indicated in comments:
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess

View reactions leading to C₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	11.4 ± 0.3	eV	N/A	N/A	L

Electron affinity determinations

EA (eV)	Method	Reference	Comment
3.2730 ± 0.0080	LPES	Arnold, Bradforth, et al., 1991	B
3.265 ± 0.022	LPES	Ervin, Gronert, et al., 1990	B
3.391 ± 0.017	LPD	Jones, Mead, et al., 1980	B
3.30 ± 0.10	LPES	Yang, Taylor, et al., 1989	EA given is Vertical Detachment Energy. probably linear structure.; B
3.540 ± 0.050	PD	Feldman, 1970	B
3.30 ± 0.20	EIAE	Locht and Momigny, 1970	From C₂H₂, C₂H₄; B
>2.89998	EIAE	Trepka and Neuert, 1963	From C₂H₄; B
>2.90 ± 0.50	EIAE	Thynne and MacNiel, 1971	From C₂H₄; B
4.0 ± 1.0	EIAE	Honig, 1954	From graphite; B

Ionization energy determinations

IE (eV)	Method	Reference	Comment
11.41 ± 0.30	CIEL	Reid, Ballantine, et al., 1995	LL
11.92 ± 0.09	DER	Plessis and Marmet, 1986	LBLHLM
12.15	DER	Huber and Herzberg, 1979	LLK
11.1 ± 0.5	EI	Gupta and Gingerich, 1979	LLK
10.9 ± 0.4	EI	Cocke and Gingerich, 1974	LLK
11.1 ± 1.0	EI	Cocke and Gingerich, 1972	LLK
12.0 ± 0.6	EI	Drowart, Burns, et al., 1959	RDSH
13.	EI	Field, Franklin, et al., 1957	RDSH

Ion clustering data

Go To: Top, Gas phase ion energetics data, Constants of diatomic molecules, References, Notes

Data compiled as indicated in comments:
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
B - John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

( • 2) + Dicarbon = ( • • 2)

By formula: (C⁺ • 2C) + C₂ = (C⁺ • C₂ • 2C)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	745.	kJ/mol	MIKES	Radi, Rincon, et al., 1989	gas phase; M

(C₂H^- • 4294967295 Dicarbon ) + = C₂H^-

By formula: (C₂H^- • 4294967295C₂) + C₂ = C₂H^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	678. ± 16.	kJ/mol	N/A	Zhou, Garand, et al., 2007	gas phase; B
Δ_rH°	535. ± 16.	kJ/mol	Ther	Ruscic and Berkowitz, 1990	gas phase; 376.7 0K; corrected with data from Gurvich, Veyts, et al.; B
Δ_rH°	703. ± 11.	kJ/mol	Ther	Bartmess, Scott, et al., 1979	gas phase; value altered from reference due to change in acidity scale; B

C₅₈⁺ + Dicarbon = (C₅₈⁺ • )

By formula: C₅₈⁺ + C₂ = (C₅₈⁺ • C₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	435. ± 50.	kJ/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

C₆₀⁺ + Dicarbon = (C₆₀⁺ • )

By formula: C₆₀⁺ + C₂ = (C₆₀⁺ • C₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	444. ± 50.	kJ/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

C₆₂⁺ + Dicarbon = (C₆₂⁺ • )

By formula: C₆₂⁺ + C₂ = (C₆₂⁺ • C₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	290. ± 50.	kJ/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

Constants of diatomic molecules

Go To: Top, Gas phase ion energetics data, Ion clustering data, References, Notes

Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through JULY, 1976

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for ¹²C₂
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
Theoretical work and potential functions Read and Vanerslice, 1962 Fougere and Nesbet, 1966 Verhaegen, Richards, et al., 1967 Verhaegen, 1968.
F ¹Π_u	[75456.9]	[1557.5] Z			1.645	0.019		0.000006		1.307	F ← X R	74532.9 Z
F ¹Π_u	↳missing citation
g ³Δ_g	[73183.6] 1	[1458.06] Z			1.5238	0.170		0.0000066		1.3579	g ← a R	71649.6 Z
g ³Δ_g	↳missing citation
f ³Σ_g^-	71045.8	1360.5 Z	14.8		1.448 2	0.04 3	0.006	0.000010		1.393	f ← a R	70188.4 Z
f ³Σ_g^-	↳missing citation
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
E ¹Σ_g⁺	55034.7	1671.5₀ Z	40.02	0.248	1.7897	0.0387 4	-0.0005₅	0.0000083	0.0000006	1.2529	E → A 5 V	46668.3 Z
E ¹Σ_g⁺	↳missing citation
d ¹Σ_u⁺	43239.4₄	1829.57 Z	13.94		1.8332 6	0.0196		0.00000732 6		1.238	D ↔ X 7	43226.74 6 Z
d ¹Σ_u⁺	↳missing citation; Norrish, Porter, et al., 1952; Messerle, 1968
e ³Π_g	40796.65 8	1106.56 Z	39.26	2.805 9	1.1922	0.0242		0.0000063	0.00000029	1.5351	e → a 10 R	39806.46 Z
e ³Π_g	↳missing citation
C' ¹Π_g	Preliminary constants from perturbations in C ¹Π_g; see Messerle and Krauss, 1967.
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
C ¹Π_g	34261.3	1809.1 Z	15.81 11		1.7834	0.018 11		0.0000068		1.2552	C → A 12 V_R	25969.19 Z
C ¹Π_g	↳Dieke and Lochte-Holtgreven, 1930; Herzberg and Sutton, 1940; Herzberg, 1945; Cisak, Dabrowska, et al., 1969
d ³Π_g	20022.50 13	1788.22 Z	16.440	-0.5067 14	1.7527 15	0.01608	-0.001274	0.0000067₄	0.000000103	1.2661	d ↔ a 16 V_R	19378.44 Z
	↳missing citation; Bugrim, Lyutyi, et al., 1965; missing citation; Phillips and Davis, 1968
											(d ← X) 17
c ³Σ_u⁺	13312.₁	1961.₆ 18	13.₇		1.87 18					1.23
A ¹Π_u	8391.00	1608.35 Z	12.07₈	-0.0119	1.613₄ 20	0.0168₆ 19	-0.000054	0.00000644 19	0.000000036	1.3184₃	A ↔ X 21 R	8268.16 Z
A ¹Π_u	↳Ballik and Ramsay, 1963
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
b ³Σ_g^-	6434.2₇	1470.4₅ Z	11.1₉	0.028 22	1.4985₂ 23	0.01634	-0.000087 24	0.00000622		1.3692₈	b → a 25 R	5632.7 Z
b ³Σ_g^-	↳missing citation
a ³Π_u	716.2₄ 26	1641.35 Z	11.67		1.6324₆ 27	0.01661		0.00000644		1.3119₀
X ¹Σ_g⁺	0	1854.71 Z	13.34₀ 28	-0.17₂ 28	1.8198₄	0.0176₅ 28	-0.00023	0.00000692 28	0.000000081	1.2425₃

Notes

A₀= -8.8+0.020J; A₁= -7.4.

Spin splitting constant λ ~0.41.

missing note

Rotational constants reevaluated; Freymark, 1951 gives B_e = 1.7930, α_e = 0.0421.

Franck-Condon factors Halmann and Laulicht, 1966; electronic transition moment Cooper and Nicholls, 1975.

From Messerle, 1968; slightly different constants in Landsverk, 1939. βe~3E-8.

Radiative lifetime τ=l4.₆ ns Smith, 1969, f₀₀= 0.055 Smith, 1969. The corresponding electronic transition moment is in only moderate agreement with Cooper and Nicholls, 1975. Franck-Condon factors Nicholls, Fraser, et al., 1959, Halmann and Laulicht, 1966.

A not determined, but much smaller than for a ³Π_u.

ω_ez_e= -0.1271.

Franck-Condon factors Nicholls, Fraser, et al., 1959, Jain, 1964, Halmann and Laulicht, 1966: el. trans. moment Cooper and Nicholls, 1975.

The ΔG and B_v curves are irregular Phillips, 1950, Messerle and Krauss, 1967, 2 and cannot be represented by the constants given without the use of higher order terms. The perturbation is strongest near v=5. Breaking-off at high J observed Messerle and Krauss, 1967 in v=0, 1, 2.

Franck-Condon factors Nicholls, Fraser, et al., 1959, Halmann and Laulicht, 1966; el. trans. moment Cooper and Nicholls, 1975.

A= -16.9.

Kini and Savadatti, 1969 have observed bands up to v'=14

Numerous small perturbations by higher levels of b ³Σ_g^- Callomon and Gilby, 1963 and X ¹Σ_g⁺ Phillips, 1968 and by unidentified states. Swan bands emitted in low-pressure oxy-acetylene flames show a distinct intensity alternation ascribed to excitation by collisions with c ³Σ_u⁺ carbon molecules Bleekrode and Nieuwpoort, 1965, Bleekrode, 1967. Under certain conditions in discharges through CO the v'=6 progression of the Swan system appears almost exclusively and was at one time considered as a separate band system, the so-called high-pressure bands of carbon Herzberg, 1946, Kunz, Harteck, et al., 1967, Meinel and Messerle, 1968*. Isotope studies Dhumwad and Narasimham, 1968 leave no doubt that the high-pressure bands are the v'=6 progression of the Swan system.

Radiative lifetime τ = 170 ns Smith, 1969, in reasonable agreement with Fink and Welge, 1967 but much shorter than Jeunehomme and Schwenker, 1965. f values obtained from the lifetime measurements as well as by other methods Fairbairn, 1966, Harrington, Modica, et al., 1966, Sviridov, Sobolev, et al., 1966, Arnold, 1968 have been reviewed in Danylewych and Nicholls, 1974. The latter authors' expression for the r dependence of the electronic transition moment was placed on an absolute scale using an average f₀₀ = 0.020. For a more recent measurement of the electronic transition moment see Cooper and Nicholls, 1975. Franck-Condon factors Nicholls, Fraser, et al., 1959, Jain, 1964, Ortenberg, 1964, Spindler, 1965, Halmann and Laulicht, 1966.

In solid matrices; tentative assignment by Barger and Broida, 1965 who also report the observation of d←a. See, however, Weltner and McLeod, 1966.

From perturbations in A ¹Π_u Ballik and Ramsay, 1963.

Very slightly revised constants in Marenin and Johnson, 1970 based on the same data.

Λ-type doubling, Δv_ef = -0.00023J(J+1). Perturbations by c ³Σ_u⁺.

f₀₀ = 0.0025; see Roux, Cerny, et al., 1976 for a comparison with other absolute measurements. Reasonably consistent with the electronic transition moment obtained by Cooper and Nicholls, 1975. Franck-Condon factors Nicholls, Fraser, et al., 1959, Ortenberg, 1964, Spindler, 1965, Halmann and Laulicht, 1966.

Callomon and Gilby, 1963

Spin-splitting parameters λ₀ = 0.11, γ₀ = -0.0036₅ Veseth, 1975. Small perturbations by levels of X ¹Σ_g⁺ Ballik and Ramsay, 1963, 2.

Callomon and Gilby, 1963.

Franck-Condon factors Halmann and Laulicht, 1966; electronic transition moment Cooper and Nicholls, 1975.

A = -15.25; Veseth, 1975 gives additional spin-coupling constants.

Λ-type doubling; see Ballik and Ramsay, 1963, 2 and Veseth, 1975.

From Ballik and Ramsay, 1963, very slightly revised constants in Marenin and Johnson, 1970 based on the same data.

Average of thermochemical values Brewer, Hicks, et al., 1962, Kordis and Gingerich, 1973. Smaller values of 6.07 and 6.11 eV have been derived on the basis of a somewhat doubtful extrapolation of the vibrational levels in d ³Π_g Messerle and Krauss, 1967, 3 and of an extrapolated limiting curve of the C ¹Π_g state Messerle and Krauss, 1967. See also Drowart, Burns, et al., 1959.

From photoionization and heat of formation of C₂N₂ Dibeler and Liston, 1967.

References

Go To: Top, Gas phase ion energetics data, Ion clustering data, Constants of diatomic molecules, Notes

Arnold, Bradforth, et al., 1991
Arnold, D.W.; Bradforth, S.E.; Kitsopoulos, T.N.; Neumark, D.M., Vibrationally Resolved Spectra of C2-C11 by Anion Photoelectron Spectroscopy, J. Chem. Phys., 1991, 95, 12, 8753, https://doi.org/10.1063/1.461211 . [all data]

Ervin, Gronert, et al., 1990
Ervin, K.M.; Gronert, S.; Barlow, S.E.; Gilles, M.K.; Harrison, A.G.; Bierbaum, V.M.; DePuy, C.H.; Lin, W.C., Bonds Strengths of Ethylene and Acetylene, J. Am. Chem. Soc., 1990, 112, 15, 5750, https://doi.org/10.1021/ja00171a013 . [all data]

Jones, Mead, et al., 1980
Jones, P.L.; Mead, R.D.; Kohler, B.E.; Rosner, S.D.; Lineberger, W.C., Photodetachment spectroscopy of C₂- autodetaching resonances, J. Chem. Phys., 1980, 73, 4419. [all data]

Yang, Taylor, et al., 1989
Yang, S.; Taylor, K.J.; Craycraft, M.J.; Conceicao, J.; Pettiette, C.L.; Cherhnovsky, O.; Smalley, R.E., UPS of 2-30 Atom Carbon Clusters: Chains and Rings, Chem. Phys. Lett., 1989, 144, 5-6, 431, https://doi.org/10.1016/0009-2614(88)87291-9 . [all data]

Feldman, 1970
Feldman, D., Photoablosung von Elektronen bei einigen Stabilen Negativen Ionen, Z. Naturfor., 1970, 25A, 621. [all data]

Locht and Momigny, 1970
Locht, R.; Momigny, J., Mass Spectrometric Determination of the Electron Affinities of Radicals, Chem. Phys. Lett., 1970, 6, 4, 273, https://doi.org/10.1016/0009-2614(70)85072-2 . [all data]

Trepka and Neuert, 1963
Trepka, L.v.; Neuert, H., Uber die Entstehenung von Negativen Ionen aus einigen Kohlenwasserstoffen und Alkoholen durch Elektronenstoss, Z. Naturfor., 1963, 18A, 1295. [all data]

Thynne and MacNiel, 1971
Thynne, J.C.J.; MacNiel, K.A.G., Negative ion formation by ethylene and 1,1-difluoroethylene, J. Phys. Chem., 1971, 75, 2584. [all data]

Honig, 1954
Honig, R.E., Mass spectrometric study of the molecular sublimation of graphite, J. Chem. Phys., 1954, 22, 126. [all data]

Reid, Ballantine, et al., 1995
Reid, C.J.; Ballantine, J.A.; Andrews, S.R.; Harris, F.M., Charge inversion of ground-state and metastable-state C₂⁺ cations formed from electroionised C₂H₂ and C₂N₂, and a re-evaluation of the carbon dimer's ionisation energy, Chem. Phys., 1995, 190, 113. [all data]

Plessis and Marmet, 1986
Plessis, P.; Marmet, P., Electroionization study of acetylene and fragment ions, Int. J. Mass Spectrom. Ion Processes, 1986, 70, 23. [all data]

Huber and Herzberg, 1979
Huber, K.P.; Herzberg, G., Molecular Spectra and Molecular Structure. IV. Constants of Diatomic Molecules,, Van Nostrand Reinhold Co., 1979, ,1. [all data]

Gupta and Gingerich, 1979
Gupta, S.K.; Gingerich, K.A., Observation and atomization energies of the gaseous uranium carbides, UC, UC₂, UC₃, UC₄, UC₅, and UC₆ by high temperature mass spectrometry, J. Chem. Phys., 1979, 71, 3072. [all data]

Cocke and Gingerich, 1974
Cocke, D.L.; Gingerich, K.A., Thermodynamic investigation of the gaseous molecules TiRh, Rh₂, and Ti₂Rh by mass spectrometry, J. Chem. Phys., 1974, 60, 1958. [all data]

Cocke and Gingerich, 1972
Cocke, D.L.; Gingerich, K.A., Mass spectrometric determination of the bond dissociation energies of the molecules CePd and CeC₂, J. Phys. Chem., 1972, 76, 2332. [all data]

Drowart, Burns, et al., 1959
Drowart, J.; Burns, R.P.; DeMaria, G.; Inghram, M.G., Mass spectrometric study of carbon vapor, J. Chem. Phys., 1959, 31, 1131. [all data]

Field, Franklin, et al., 1957
Field, F.H.; Franklin, J.L.; Lampe, F.W., Reactions of gaseous ions. II. Acetylene, J. Am. Chem. Soc., 1957, 79, 2665. [all data]

Radi, Rincon, et al., 1989
Radi, P.P.; Rincon, M.E.; Hsu, M.T.; Brodbelt-Lustig, J.; Kemper, P.; Bowers, M.T., Structure, Reactivity and Energetics of Covalently Bound Carbon Cluster Ions, C5+ to C11+: Experiment and Theory, J. Phys. Chem., 1989, 93, 16, 6187, https://doi.org/10.1021/j100353a045 . [all data]

Zhou, Garand, et al., 2007
Zhou, J.; Garand, E.; Neumark, D.M., Vibronic structure in C2H and C2D from anion slow electron velocity-map imaging spectroscopy, J. Chem. Phys., 2007, 127, 11, 114313, https://doi.org/10.1063/1.2768932 . [all data]

Ruscic and Berkowitz, 1990
Ruscic, B.; Berkowitz, J., Photoion-pair Formation and Photoelectron-induced Dissociative Attachment in C2H2: D0(HCC-H), J. Chem. Phys., 1990, 93, 8, 5586, https://doi.org/10.1063/1.459629 . [all data]

Gurvich, Veyts, et al.
Gurvich, L.V.; Veyts, I.V.; Alcock, C.B., Hemisphere Publishing, NY, 1989, V. 1 2, Thermodynamic Properties of Individual Substances, 4th Ed. [all data]

Bartmess, Scott, et al., 1979
Bartmess, J.E.; Scott, J.A.; McIver, R.T., Jr., The gas phase acidity scale from methanol to phenol, J. Am. Chem. Soc., 1979, 101, 6047. [all data]

Radi, Hsu, et al., 1990
Radi, P.R.; Hsu, M.T.; Rincon, M.E.; Kemper, P.R.; Bowers, M.T., On the Structure, Reactivity and Relative Stability of the Large Carbon Cluster Ions C62+, C60+ and C58+, Chem. Phys. Lett., 1990, 174, 3-4, 223, https://doi.org/10.1016/0009-2614(90)85336-B . [all data]

Read and Vanerslice, 1962
Read, S.M.; Vanerslice, J.T., Potential energy curves for C₂, J. Chem. Phys., 1962, 36, 2366. [all data]

Fougere and Nesbet, 1966
Fougere, P.F.; Nesbet, R.K., Electronic structure of C₂, J. Chem. Phys., 1966, 44, 285. [all data]

Verhaegen, Richards, et al., 1967
Verhaegen, G.; Richards, W.G.; Moser, C.M., Low-lying valence levels of BN and C₂. The ground state of BN, J. Chem. Phys., 1967, 46, 160. [all data]

Verhaegen, 1968
Verhaegen, G., Theoretical calculation of the electronic states of C₂⁺, J. Chem. Phys., 1968, 49, 4696. [all data]

Norrish, Porter, et al., 1952
Norrish, R.G.W.; Porter, G.; Thrush, B.A., Detection of diatomic radical absorption spectra during combustion, Nature (London), 1952, 169, 582. [all data]

Messerle, 1968
Messerle, G., Anregung hoher Rotationsniveaus von C₂-Banden, Z. Naturforsch. A, 1968, 23, 470. [all data]

Messerle and Krauss, 1967
Messerle, G.; Krauss, L., Die Dissoziation des C₂ - Molekuls durch Rotation, Z. Naturforsch. A, 1967, 22, 2023. [all data]

Dieke and Lochte-Holtgreven, 1930
Dieke, G.H.; Lochte-Holtgreven, W., Uber einige banden des kohlenstoffmolekuls, Z. Phys., 1930, 62, 767. [all data]

Herzberg and Sutton, 1940
Herzberg, G.; Sutton, R.B., Tail bands of the deslandres-d'azambuja system of the C₂ molecule, Can. J. Res. Sect. A, 1940, 18, 74. [all data]

Herzberg, 1945
Herzberg, G., Molecular spectra and molecular structure. II. Infrared and Raman spectra of polyatomic molecules, Pub. D. Van Nostrand Company, Inc., Princeton, New Jersey, 1945, 0. [all data]

Cisak, Dabrowska, et al., 1969
Cisak, H.; Dabrowska, K.; Rytel, M., The Deslandres-d'Azambuja bands of isotopic C₂ molecules, Acta Phys. Pol., 1969, 36, 497. [all data]

Bugrim, Lyutyi, et al., 1965
Bugrim, E.D.; Lyutyi, A.I.; Rossikhin, V.S.; Tsikora, I.L., New bands in the Swan system of the C₂ molecule, Opt. Spectrosc. Engl. Transl., 1965, 19, 292, In original 524. [all data]

Phillips and Davis, 1968
Phillips, J.G.; Davis, S.P., Berkely analyses of molecular spectra, Pub. University of California Press, Berkeley and Los Angeles, 1968, 0. [all data]

Ballik and Ramsay, 1963
Ballik, E.A.; Ramsay, D.A., An extension of the Phillips system of C₂ and a survey of C₂ states, Astrophys. J., 1963, 137, 84. [all data]

Freymark, 1951
Freymark, H., Uber ein neues Bandensystem des C₂-Molekuls im Ultravioletten, Ann. Phys. (Neue Folge), 1951, 8, 221. [all data]

Halmann and Laulicht, 1966
Halmann, M.; Laulicht, I., Isotope effects on vibrational transition probabilities. IV. Electronic transitions of isotopic C₂, CO, CN, H₂, and CH molecules, Astrophys. J. Suppl. Ser., 1966, 12, 307. [all data]

Cooper and Nicholls, 1975
Cooper, D.M.; Nicholls, R.W., Measurments of the electronic transition moments of C₂-band systems, J. Quant. Spectrosc. Radiat. Transfer, 1975, 15, 139. [all data]

Landsverk, 1939
Landsverk, O.G., A ¹Σ→¹Σ transition of the C₂ molecule, Phys. Rev., 1939, 56, 769-777. [all data]

Smith, 1969
Smith, W.H., Transition probabilities for the Swan and Mulliken C₂ bands, Astrophys. J., 1969, 156, 791. [all data]

Nicholls, Fraser, et al., 1959
Nicholls, R.W.; Fraser, P.A.; Jarmain, W.R., Transition probability parameters of molecular spectra arising from combustion processes, Combust. Flame, 1959, 3, 13. [all data]

Jain, 1964
Jain, D.C., Transition probability parameters of the Swan and the Fox-Herzberg band systems of the C₂ molecule, J. Quant. Spectrosc. Radiat. Transfer, 1964, 4, 427. [all data]

Phillips, 1950
Phillips, J.G., On the identification of the 3670 A band of the C₂ molecule, Astrophys. J., 1950, 112, 131. [all data]

Messerle and Krauss, 1967, 2
Messerle, G.; Krauss, L., Ein neues c'¹Π_g - b¹Π_u - Bandensystem des C₂ - Molekuls, Z. Naturforsch. A, 1967, 22, 2015. [all data]

Kini and Savadatti, 1969
Kini, K.S.; Savadatti, M.I., Extension of the C₂(A³Π_g-X'³Π_u) band system, J. Phys. B:, 1969, 2, 307. [all data]

Callomon and Gilby, 1963
Callomon, J.H.; Gilby, A.C., New observations on the Swan bands of C₂, Can. J. Phys., 1963, 41, 995. [all data]

Phillips, 1968
Phillips, J.G., Perturbations in the Swan system of the C₂ molecule, J. Mol. Spectrosc., 1968, 28, 233. [all data]

Bleekrode and Nieuwpoort, 1965
Bleekrode, R.; Nieuwpoort, W.C., Absorption and emission measurements of C₂ and CH electronic bands in low-pressure oxyacetylene flames, J. Chem. Phys., 1965, 43, 3680. [all data]

Bleekrode, 1967
Bleekrode, R., Absorption and emission spectroscopy of C₂, CH and OH in low-pressure oxyacetylene flames, Philips Res. Rep. Suppl., 1967, 7, 1. [all data]

Herzberg, 1946
Herzberg, G., On the high pressure bands of carbon and the formation of C₂ molecules, Phys. Rev., 1946, 70, 762. [all data]

Kunz, Harteck, et al., 1967
Kunz, C.; Harteck, P.; Dondes, S., Mechanism for excitation of the C₂ high-pressure bands (C + C₂O → C₂(A³Π) + CO), J. Chem. Phys., 1967, 46, 4157. [all data]

Meinel and Messerle, 1968
Meinel, H.; Messerle, G., Investigation of the fine structure of the C₂ high-pressure bands, Astrophys. J., 1968, 154, 381. [all data]

Dhumwad and Narasimham, 1968
Dhumwad, R.K.; Narasimham, N.A., Isotope shift studies of the high-pressure carbon bands, Can. J. Phys., 1968, 46, 1254. [all data]

Fink and Welge, 1967
Fink, E.H.; Welge, K.H., Lifetime measurements on CH(A²Δ), CH(B²Σ^-), and C₂(A³Π_g) by the phase-shift method, J. Chem. Phys., 1967, 46, 4315. [all data]

Jeunehomme and Schwenker, 1965
Jeunehomme, M.; Schwenker, R.P., Focused laser-beam experiment and the oscillator strength of the Swan system, J. Chem. Phys., 1965, 42, 2406. [all data]

Fairbairn, 1966
Fairbairn, A.R., A shock-tube study of the oscillator strength of the C₂ Swan bands, J. Quant. Spectrosc. Radiat. Transfer, 1966, 6, 325. [all data]

Harrington, Modica, et al., 1966
Harrington, J.A.; Modica, A.P.; Libby, D.R., Shock-tube determination of the C₂(A³Π → X³Π) and CF(A²Σ⁺ → X²Π) band-system oscillator strengths, J. Chem. Phys., 1966, 44, 3380. [all data]

Sviridov, Sobolev, et al., 1966
Sviridov, A.G.; Sobolev, N.N.; Novgorodov, M.Z., Determination of the matrix elements of the dipole moments of the electronic transitions of the Swan band system of the C₂ molecule. II. Absorption method, J. Quant. Spectrosc. Radiat. Transfer, 1966, 6, 337. [all data]

Arnold, 1968
Arnold, J.O., A shock tube determination of the electronic transition moment of the C₂(Swan), bands, J. Quant. Spectrosc. Radiat. Transfer, 1968, 8, 1781. [all data]

Danylewych and Nicholls, 1974
Danylewych, L.L.; Nicholls, R.W., Intensity measurements on the C₂ (d³Π_g-a³Π_u) Swan band system. I. Intercept and partial band methods, Proc. R. Soc. London A, 1974, 339, 197-212. [all data]

Ortenberg, 1964
Ortenberg, F.S., Calculation of Franck-Condon factors for the NO, C₂, and CO band systems, Opt. Spectrosc. Engl. Transl., 1964, 16, 398, In original 729. [all data]

Spindler, 1965
Spindler, R.J., Franck-Condon factors based on RKR potentials with applications to radiative absorption coefficients, J. Quant. Spectrosc. Radiat. Transfer, 1965, 5, 165. [all data]

Barger and Broida, 1965
Barger, R.L.; Broida, H.P., Spectra of C₂ in solidified gases at 4º and 20 ºK, J. Chem. Phys., 1965, 43, 7, 2371-2376. [all data]

Weltner and McLeod, 1966
Weltner, W., Jr.; McLeod, D., Jr., Spectroscopy of Carbon Vapor Condensed in Rare-Gas Matrices at 4°K. III, J. Chem. Phys., 1966, 45, 8, 3096, https://doi.org/10.1063/1.1728066 . [all data]

Marenin and Johnson, 1970
Marenin, I.R.; Johnson, H.R., New molecular constants for the Phillips system of C₂, J. Quant. Spectrosc. Radiat. Transfer, 1970, 10, 305. [all data]

Roux, Cerny, et al., 1976
Roux, F.; Cerny, D.; d'Incan, J., Experimental oscillator strengths in the C₂(A¹Π_u-X¹Σ_g⁺) Phillips band system, Astrophys. J., 1976, 204, 940. [all data]

Veseth, 1975
Veseth, L., Molecular parameters for the a³Π_u and b³Σ_g^- states in C₂, Can. J. Phys., 1975, 53, 299. [all data]

Ballik and Ramsay, 1963, 2
Ballik, E.A.; Ramsay, D.A., The A'³Σ_g^--X'³Π_u band system of the C₂ molecule, Astrophys. J., 1963, 137, 61. [all data]

Brewer, Hicks, et al., 1962
Brewer, L.; Hicks, W.T.; Krikorian, O.H., Heat of sublimation and dissociation energy of gaseous C₂, J. Chem. Phys., 1962, 36, 182. [all data]

Kordis and Gingerich, 1973
Kordis, J.; Gingerich, K.A., Gaseous phosphorus compounds. IX. Mass spectrometric studies of equilibria in the carbon-phosporus system, J. Chem. Phys., 1973, 58, 5058. [all data]

Messerle and Krauss, 1967, 3
Messerle, G.; Krauss, L., Spektroskopische Bestimmung der Dissoziationsenergie des C₂-Molekuls aus den ³Π_g - Termen, Z. Naturforsch. A, 1967, 22, 1744. [all data]

Dibeler and Liston, 1967
Dibeler, V.H.; Liston, S.K., Mass-spectrometric study of photoionization. VIII.Dicyanogen and the cyanogen halides, J. Chem. Phys., 1967, 47, 4548. [all data]

Notes

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Symbols used in this document:

EA Electron affinity

IE (evaluated) Recommended ionization energy

Δ_rH° Enthalpy of reaction at standard conditions
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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EA	Electron affinity
IE (evaluated)	Recommended ionization energy
Δ_rH°	Enthalpy of reaction at standard conditions