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Experimental data for C2 (Carbon diatomic)

22 02 02 11 45
Other names
Carbon (C2); Carbon dimer; Dicarbon;
State Conformation
1Σg+ D*H
Enthalpy of formation (Hfg), Entropy, Integrated heat capacity (0 K to 298.15 K) (HH), Heat Capacity (Cp)
Property Value Uncertainty units Reference Comment
Hfg(298.15K) enthalpy of formation 830.46 10.00 kJ mol-1 Gurvich
Hfg(0K) enthalpy of formation 822.39 10.00 kJ mol-1 Gurvich
Entropy (298.15K) entropy 197.10   J K-1 mol-1 Gurvich
Integrated Heat Capacity (0 to 298.15K) integrated heat capacity 10.17   kJ mol-1 Gurvich
Heat Capacity (298.15K) heat capacity 43.55   J K-1 mol-1 Gurvich
Information can also be found for this species in the NIST Chemistry Webbook
Vibrational levels (cm-1) vibrations
Mode Number Symmetry Frequency Intensity Comment Description
Fundamental(cm-1) Harmonic(cm-1) Reference (km mol-1) unc. Reference
1 Σg 1827 1855 2007Iri:389      

Detailed diatomic data
ωe ωexe ωeye Be αe ZPE reference
1855.066 13.6007 -0.116 1.820053 0.0179143 923.9669 2007Iri:389

vibrational zero-point energy: 913.7 cm-1 (from fundamental vibrations)
Calculated vibrational frequencies for C2 (Carbon diatomic).
Rotational Constants (cm-1) rotational constants
See section I.F.4 to change rotational constant units
A B C reference comment
  1.82005   2007Iri:389

Calculated rotational constants for C2 (Carbon diatomic).
Product of moments of inertia moments of inertia
9.262164amu Å2   1.538043E-39gm cm2
Geometric Data
picture of Carbon diatomic

Point Group D∞h

Internal coordinates
distances (r) in Å, angles (a) in degrees, dihedrals (d) in degrees
Description Value unc. Connectivity Reference Comment
Atom 1 Atom 2 Atom 3 Atom 4
rCC 1.243   1 2 1979HUB/HER re

Atom x (Å) y (Å) z (Å)
C1 0.0000 0.0000 0.0000
C2 0.0000 0.0000 1.2425

Atom - Atom Distances bond lengths
Distances in Å
  C1 C2
C1   1.2425
C2 1.2425  

Calculated geometries for C2 (Carbon diatomic).

Bond descriptions

Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
C#C 1

Atom 1 Atom 2
C1 C2
Electronic energy levels (cm-1)
Energy (cm-1) Degeneracy reference description
0 1 Gurvich 1Σg+
716.24 6 Gurvich 3Πu
6434.27 3 Gurvich 3Σg-
8391 2 Gurvich 1Πu

Ionization Energies (eV)
Ionization Energy I.E. unc. vertical I.E. v.I.E. unc. reference
11.400 0.300     webbook

Electron Affinity (eV)
Electron Affinity unc. reference
3.273 0.008 webbook
Dipole, Quadrupole and Polarizability
Electric dipole moment dipole
State Config State description Conf description Exp. min. Dipole (Debye) Reference comment Point Group Components
x y z total dipole quadrupole
1 1 1Σg+ D∞h True       0.000 NSRDS-NBS10   D∞h 0 1
2 1 3Πu D∞h True           D∞h 0 1
3 1 3Σg- D∞h True           D∞h 0 1
4 1 1Πu D∞h True           D∞h 0 1
Experimental dipole measurement abbreviations: MW microwave; DT Dielectric with Temperature variation; DR Indirect (usually an upper limit); MB Molecular beam
Calculated electric dipole moments for C2 (Carbon diatomic).
Electric quadrupole moment quadrupole
State Config State description Conf description Exp. min. Quadrupole (D Å) Reference comment Point Group Components
xx yy zz dipole quadrupole
1 1 1Σg+ D∞h True       D∞h 0 1
2 1 3Πu D∞h True       D∞h 0 1
3 1 3Σg- D∞h True       D∞h 0 1
4 1 1Πu D∞h True       D∞h 0 1

Calculated electric quadrupole moments for C2 (Carbon diatomic).

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squib reference DOI
1979HUB/HER Huber, K.P.; Herzberg, G., Molecular Spectra and Molecular Structure. IV. Constants of Diatomic Molecules, Van Nostrand Reinhold Co., 1979 10.1007/978-1-4757-0961-2
2007Iri:389 KK Irikura "Experimental Vibrational Zero-Point Energies: Diatomic Molecules" J. Phys. Chem. Ref. Data 36(2), 389, 2007 10.1063/1.2436891
Gurvich Gurvich, L.V.; Veyts, I. V.; Alcock, C. B., Thermodynamic Properties of Individual Substances, Fouth Edition, Hemisphere Pub. Co., New York, 1989  
NSRDS-NBS10 R. D. Nelson Jr., D. R. Lide, A. A. Maryott "Selected Values of electric dipole moments for molecules in the gas phase" NSRDS-NBS10, 1967 10.6028/NBS.NSRDS.10
webbook NIST Chemistry Webbook ( 10.18434/T4D303

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