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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Gas phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	200.22	kcal/mol	Review	Chase, 1998	Data last reviewed in December, 1969
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	47.655	cal/mol*K	Review	Chase, 1998	Data last reviewed in December, 1969

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
C_p = heat capacity (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.

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View table.

Temperature (K)	298. to 700.	700. to 6000.
A	29.61501	7.290651
B	-83.17560	1.301581
C	115.9410	-0.203961
D	-55.64039	0.015689
E	-0.296438	0.194730
F	193.1830	198.7520
G	101.9630	57.45791
H	200.2240	200.2240
Reference	Chase, 1998	Chase, 1998
Comment	Data last reviewed in December, 1969	Data last reviewed in December, 1969

Reaction thermochemistry data

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

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

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

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

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	162.0 ± 3.8	kcal/mol	N/A	Zhou, Garand, et al., 2007	gas phase; B
Δ_rH°	127.8 ± 3.9	kcal/mol	Ther	Ruscic and Berkowitz, 1990	gas phase; 376.7 0K; corrected with data from Gurvich, Veyts, et al.; B
Δ_rH°	168.0 ± 2.7	kcal/mol	Ther	Bartmess, Scott, et al., 1979	gas phase; value altered from reference due to change in acidity scale; B

( • 2) + Dicarbon = ( • • 2)

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

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	178.	kcal/mol	MIKES	Radi, Rincon, et al., 1989	gas phase; M

C₆₂⁺ + Dicarbon = (C₆₂⁺ • )

By formula: C₆₂⁺ + C₂ = (C₆₂⁺ • C₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	69. ± 12.	kcal/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

C₅₈⁺ + Dicarbon = (C₅₈⁺ • )

By formula: C₅₈⁺ + C₂ = (C₅₈⁺ • C₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	104. ± 12.	kcal/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°	106. ± 12.	kcal/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

Gas phase ion energetics data

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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

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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°	178.	kcal/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°	162.0 ± 3.8	kcal/mol	N/A	Zhou, Garand, et al., 2007	gas phase; B
Δ_rH°	127.8 ± 3.9	kcal/mol	Ther	Ruscic and Berkowitz, 1990	gas phase; 376.7 0K; corrected with data from Gurvich, Veyts, et al.; B
Δ_rH°	168.0 ± 2.7	kcal/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°	104. ± 12.	kcal/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°	106. ± 12.	kcal/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°	69. ± 12.	kcal/mol	MIKES	Radi, Hsu, et al., 1990	gas phase; M

Constants of diatomic molecules

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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 thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, Constants of diatomic molecules, NIST Free Links, Notes

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [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, 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]

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]

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]

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
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Messerle and Krauss, 1967, 2
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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
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Phillips, 1968
Phillips, J.G., Perturbations in the Swan system of the C₂ molecule, J. Mol. Spectrosc., 1968, 28, 233. [all data]

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Notes

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Symbols used in this document:

EA	Electron affinity
IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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