Oxygen

• Formula: O₂
• Molecular weight: 31.9988
• IUPAC Standard InChI: InChI=1S/O2/c1-2 Copy

  
• IUPAC Standard InChIKey: MYMOFIZGZYHOMD-UHFFFAOYSA-N Copy
• CAS Registry Number: 7782-44-7
• 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.
• Other names: Molecular oxygen; Oxygen molecule; Pure oxygen; O2; Liquid oxygen; UN 1072; UN 1073; Dioxygen
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Phase change data
  • Gas phase ion energetics data
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 70
  • Henry's Law data
  • Ion clustering data
  • Constants of diatomic molecules
  • Fluid Properties
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Gas Phase Kinetics Database
• Options:
  • Switch to SI units

Data at NIST subscription sites:

• NIST / TRC Web Thermo Tables, "lite" edition (thermophysical and thermochemical data)
• NIST / TRC Web Thermo Tables, professional edition (thermophysical and thermochemical data)

NIST subscription sites provide data under the NIST Standard Reference Data Program, but require an annual fee to access. The purpose of the fee is to recover costs associated with the development of data collections included in such sites. Your institution may already be a subscriber. Follow the links above to find out more about the data in these sites and their terms of usage.

Gas phase thermochemistry data

Go To: Top, Phase change data, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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.

View plot Requires a JavaScript / HTML 5 canvas capable browser.

View table.

Phase change data

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Mass spectrum (electron ionization), References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
    P = vapor pressure (atm)
    T = temperature (K)

View plot Requires a JavaScript / HTML 5 canvas capable browser.

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Phase change data, Mass spectrum (electron ionization), References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

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

View reactions leading to O₂⁺ (ion structure unspecified)

Electron affinity determinations

Proton affinity at 298K

Ionization energy determinations

Appearance energy determinations

Anion protonation reactions

 +  =

By formula: O₂^- + H⁺ = HO₂

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Phase change data, Gas phase ion energetics data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

Notice: This spectrum may be better viewed with a Javascript and HTML 5 enabled browser.

For Zoom

1.) Enter the desired X axis range (e.g., 100, 200)

2.) Check here for automatic Y scaling

3.) Press here to zoom

Additional Data

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Gas phase ion energetics data, Mass spectrum (electron ionization), Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Cox, Wagman, et al., 1984
Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

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

Streng, 1971
Streng, A.G., Miscibility and Compatibility of Some Liquid and Solidified Gases at Low Temperature, J. Chem. Eng. Data, 1971, 16, 357. [all data]

Henning and Otto, 1936
Henning, F.; Otto, J., Vapor pressure curves and triple points in the temperature region from 14 to 90 k, Phys. Z., 1936, 37, 633-8. [all data]

Pentermann and Wagner, 1978
Pentermann, W.; Wagner, W., New pressure-density-temperature measurements and new rational equations for the saturated liquid and vapor densities of oxygen, J. Chem. Thermodyn., 1978, 10, 1161-1172. [all data]

Wagner, Ewers, et al., 1976
Wagner, W.; Ewers, J.; Pentermann, W., A New Vapor-Pressure Measurement and a New Rational Vapor-Pressure Equation for Oxygen, J. Chem. Thermodyn., 1976, 8, 1049. [all data]

Cardoso, 1915
Cardoso, E., Study of the Critical Point of Several Difficultly LIquifiable Gases: Nitrogen, Carbon Monoxide, Oxygen and Methane, J. Chim. Phys. Phys.-Chim. Biol., 1915, 13, 312. [all data]

Brower and Thodos, 1968
Brower, G.T.; Thodos, G., Vapor Pressures of Liquid Oxygen Between the Triple Point and Critical Point, J. Chem. Eng. Data, 1968, 13, 2, 262-264, https://doi.org/10.1021/je60037a038 . [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

Ervin, Anusiewicz, et al., 2003
Ervin, K.M.; Anusiewicz, W.; Skurski, P.; Simons, J.; Lineberger, W.C., The only stable state of O-2(-) is the X (2)Pi(g) ground state and it (still!) has an adiabatic electron detachment energy of, J. Phys. Chem. A, 2003, 107, 41, 8521-8529, https://doi.org/10.1021/jp0357323 . [all data]

Travers, Cowles, et al., 1989
Travers, M.J.; Cowles, D.C.; Ellison, G.B., Reinvestigation of the Electron Affinities of O2 and NO, Chem. Phys. Lett., 1989, 164, 5, 449, https://doi.org/10.1016/0009-2614(89)85237-6 . [all data]

Celotta, Bennett, et al., 1972
Celotta, R.J.; Bennett, R.A.; Hall, J.L.; Siegel, M.W.; Levine, J., Molecular photodetachment spectrometry. II. The electron affinity of O₂ and the structure of O₂-, Phys. Rev. A:, 1972, 6, 631. [all data]

Chen and Wentworth, 1983
Chen, E.C.M.; Wentworth, W.E., Determination of molecular electron affinities using the electron capture detector in the pulse sampling mode at steady state, J. Phys. Chem., 1983, 87, 45. [all data]

Tiernan and Wu, 1978
Tiernan, T.O.; Wu, R.L.C., Thermochemical Data for Molecular Negative Ions from Collisional Dissociation Thresholds, Adv. Mass Spectrom., 1978, 7A, 136. [all data]

Durup, Parlant, et al., 1977
Durup, M.; Parlant, G.; Appell, J.; Durup, J.; Ozenne, J.-B., Translational spectroscopy of neutralization-reionization double collision processes of Ar⁺ ions at keV energies, Chem. Phys., 1977, 25, 245. [all data]

Burrow, 1974
Burrow, P.D., Temporary negative ion formation in NO and O₂, Chem. Phys. Lett., 1974, 26, 265. [all data]

Baeda, 1972
Baeda, A.P.M., The adiabatic electron affinities of Cl₂, Br₂, I₂, IBr, NO₂, and O₂, Physica, 1972, 59, 541. [all data]

Celotta, Bennett, et al., 1971
Celotta, R.J.; Bennett, R.A.; Hall, J.L.; Levine, J.; Siegel, M.W., Electron affinity of O₂ by laser photodetachment, Bull. Am. Phys. Soc., 1971, 16, 212. [all data]

Nalley and Compton, 1971
Nalley, S.J.; Compton, R.N., Collisional ionization of cesium by oxygen: The electron affinity of O₂, Chem. Phys. Lett., 1971, 9, 529. [all data]

Tiernan, Hughes, et al., 1971
Tiernan, T.O.; Hughes, B.M.; Lifschitz, C., Electron affinities from endothermic negative ion charge transfer reactions. II. O₂, J. Chem. Phys., 1971, 55, 5692. [all data]

Lacmann and Herschbach, 1970
Lacmann, K.; Herschbach, D.R., Collisional Excitation and Ionization of K Atoms by Diatomic Molecules: Role of Ion-pair States, Chem. Phys. Lett., 1970, 6, 2, 106, https://doi.org/10.1016/0009-2614(70)80144-0 . [all data]

Pack and Phelps, 1966
Pack, J.L.; Phelps, A.V., Electron Attachment and Detachment. I. Pure O₂ at Low Energy, J. Chem. Phys., 1966, 44, 5, 1870, https://doi.org/10.1063/1.1726956 . [all data]

Berkowitz, Chupka, et al., 1971
Berkowitz, J.; Chupka, W.A.; Gutman, D., Electron Affinities of O₂, O₃, NO, NO₂, and NO₃ by Endothermic Charge Transfer, J. Chem. Phys., 1971, 55, 6, 2733, https://doi.org/10.1063/1.1676488 . [all data]

Chantry, 1971
Chantry, P.J., Doppler broadening in beam experiments, J. Chem. Phys., 1971, 55, 2746. [all data]

Chen and Chen, 2003
Chen, E.S.; Chen, E.C.M., Semiempirical characterization of homonuclear diatomic ions: 6. Group VI and VII anions, J. Phys. Chem. A, 2003, 107, 1, 169-177, https://doi.org/10.1021/jp0268922 . [all data]

Bailey and Mahadevan, 1970
Bailey, T.L.; Mahadevan, P., Electron Transfer and Detachment in Collisions of Low Energy Negative Ions with O₂, J. Chem. Phys., 1970, 52, 1, 179, https://doi.org/10.1063/1.1672663 . [all data]

Vogt, Hauffle, et al., 1970
Vogt, D.; Hauffle, B.; Neuert, H., Ladungsaustausch-Reaktionen Einiger Negativer Ionen mit O₂ und die Elektronenaffinitat des O₂, Z. Phys., 1970, 232, 5, 439, https://doi.org/10.1007/BF01395674 . [all data]

Stockdale, Compton, et al., 1969
Stockdale, J.A.D.; Compton, R.N.; Hurst, G.S.; Reinhardt, P.W., Collisions of Monoenergetic Electrons with NO₂: Possible Lower Limits to the Electron Affinities of O₂ and NO, J. Chem. Phys., 1969, 50, 5, 2176, https://doi.org/10.1063/1.1671347 . [all data]

Burch, Smith, et al., 1958
Burch, D.S.; Smith, S.J.; Branscomb, L.M., Photodetachment of O₂^-., Phys. Rev., 1958, 112, 1, 171, https://doi.org/10.1103/PhysRev.112.171 . [all data]

Litorja and Ruscic, 1998
Litorja, M.; Ruscic, B., A photoionization study of the hydroperoxyl radical, HO2, and hydrogen peroxide, H2O2, J. Electron Spectroscopy and Related Phenomena, 1998, 97, 131. [all data]

Tonkyn, Winniczek, et al., 1989
Tonkyn, R.G.; Winniczek, J.W.; White, M.G., Rotationally resolved photoionization of O₂ near threshold, Chem. Phys. Lett., 1989, 164, 137. [all data]

Grade, Wienecke, et al., 1983
Grade, M.; Wienecke, J.; Rosinger, W.; Hirschwald, W., Electron impact investigation of the molecules SeS(g) and TeSe(g) under high-temperature equilibrium conditions, Ber. Bunsen-Ges. Phys. Chem., 1983, 87, 355. [all data]

Gomez, Chatillon, et al., 1982
Gomez, M.; Chatillon, C.; Allibert, M., Thermodynamics of gaseous and condensed indium oxides by mass spectrometry with controlled oxygen oressure, J. Chem. Thermodyn., 1982, 14, 447. [all data]

Farber, Srivastava, et al., 1982
Farber, M.; Srivastava, R.D.; Moyer, J.W., Mass spectrometric determination of the thermodynamics of potassium hydroxide and minor potassium-containing species required in magnetohydrodynamic power systems, J. Chem. Thermodyn., 1982, 14, 1103. [all data]

MacNeil and Dixon, 1977
MacNeil, K.A.G.; Dixon, R.N., High-resolution photoelectron spectroscopy of methanol and its deuterated derivatives: Internal rotation in the ground ionic state, J. Electron Spectrosc. Relat. Phenom., 1977, 11, 315. [all data]

Kronebusch and Berkowitz, 1976
Kronebusch, P.L.; Berkowitz, J., Photodissociative ionization in the 21-41 eV region: O₂, N₂, CO, NO, CO₂, H₂O, NH₃ and CH₄, Int. J. Mass Spectrom. Ion Phys., 1976, 22, 283. [all data]

Samson and Gardner, 1975
Samson, J.A.R.; Gardner, J.L., On the ionization potential of molecular oxygen, Can. J. Phys., 1975, 53, 1948. [all data]

Hildenbrand, 1975
Hildenbrand, D.L., Vertical ionization potential of the CF₂ radical, Chem. Phys. Lett., 1975, 32, 30. [all data]

Bennett, Lin, et al., 1974
Bennett, S.L.; Lin, S.-S.; Gilles, P.W., High-temperature vaporization of ternary systems. I. Mass spectrometry of oxygen-rich vanadium-tungsten-oxygen species, J. Phys. Chem., 1974, 78, 266. [all data]

Tanaka and Tanaka, 1973
Tanaka, K.; Tanaka, I., Photoelectron spectra from some autoionizing state of O₂ near the ionization threshold, J. Chem. Phys., 1973, 59, 5042. [all data]

Natalis, 1973
Natalis, P., Contribution a la spectroscopie photoelectronique. Effets de l'autoionisation dans less spectres photoelectroniques de molecules diatomiques et triatomiques, Acad. R. Belg. Mem. Cl. Sci. Collect. 8, 1973, 41, 1. [all data]

Dromey, Morrison, et al., 1973
Dromey, R.G.; Morrison, J.D.; Peel, J.B., Time-averaged and deconvoluted photoelectron spectrum of the first band of O₂, Chem. Phys. Lett., 1973, 23, 30. [all data]

Vilesov and Lopatin, 1972
Vilesov, F.I.; Lopatin, S.N., Photoelectron spectrometer, Zh. Tekh. Fiz., 1972, 42, 176. [all data]

Dibeler and Walker, 1967
Dibeler, V.H.; Walker, J.A., Mass spectrometric study of the photoionization of small polyatomic molecules, Advan. Mass Spectrom., 1967, 4, 767. [all data]

Samson and Cairns, 1966
Samson, J.A.R.; Cairns, R.B., Ionization potential of O₂, J. Opt. Soc. Am., 1966, 56, 769. [all data]

Brehm, 1966
Brehm, B., Massenspektrometrische Untersuchung der Photoionisation von Molekulen, Z. Naturforsch., 1966, 21a, 196. [all data]

Nicholson, 1963
Nicholson, A.J.C., Photo-ionization efficiency curves. Measurement of ionization potentials and interpretation of fine structure, J. Chem. Phys., 1963, 39, 954. [all data]

Watanabe, 1957
Watanabe, K., Ionization potentials of some molecules, J. Chem. Phys., 1957, 26, 542. [all data]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Banna and Shirley, 1976
Banna, M.S.; Shirley, D.A., Molecular photoelectron spectroscopy at 132.3 eV: N₂, CO, C₂H₄ and O₂, J. Electron Spectrosc. Relat. Phenom., 1976, 8, 255. [all data]

Blyth, Powis, et al., 1981
Blyth, R.C.G.; Powis, I.; Danby, C.J., Competing pre-dissociations of O₂⁺(B ²Σ_g^-), Chem. Phys. Lett., 1981, 84, 272. [all data]

Oertel, Schenk, et al., 1980
Oertel, H.; Schenk, H.; Baumgartel, H., Ion pair formation from photon irradiation of O₂, NO and CO in 17-30 eV, Chem. Phys., 1980, 46, 251. [all data]

Locht and Schopman, 1974
Locht, R.; Schopman, J., The dissociative ionization in oxygen, Int. J. Mass Spectrom. Ion Phys., 1974, 15, 361. [all data]

Locht and Momigny, 1971
Locht, R.; Momigny, J., Mass spectrometric study of ion-pair processes in diatomic molecules: H₂, CO, NO and O₂, Int. J. Mass Spectrom. Ion Phys., 1971, 7, 121. [all data]

Elder, Villarejo, et al., 1965
Elder, F.A.; Villarejo, D.; Inghram, M.G., Electron affinity of oxygen, J. Chem. Phys., 1965, 43, 758. [all data]

Weissler, Samson, et al., 1959
Weissler, G.L.; Samson, J.A.R.; Ogawa, M.; Cook, G.R., Photoionization analysis by mass spectroscopy, J. Opt. Soc. Am., 1959, 49, 338. [all data]

Frost and McDowell, 1959
Frost, D.C.; McDowell, C.A., Recent electron impact studies on simple molecules (O₂, Cl₂, I₂), Advan. Mass Spectrom., 1959, 1, 413. [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Gas phase ion energetics data, Mass spectrum (electron ionization), References

• Symbols used in this document:
  

  AE	Appearance energy
  EA	Electron affinity
  IE (evaluated)	Recommended ionization energy
  Pc	Critical pressure
  S°gas,1 bar	Entropy of gas at standard conditions (1 bar)
  Tboil	Boiling point
  Tc	Critical temperature
  Tfus	Fusion (melting) point
  Ttriple	Triple point temperature
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ρc	Critical density

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
• The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
• Customer support for NIST Standard Reference Data products.