Hydrogen

• Formula: H₂
• Molecular weight: 2.01588
• IUPAC Standard InChI: InChI=1S/H2/h1H Copy

  
• IUPAC Standard InChIKey: UFHFLCQGNIYNRP-UHFFFAOYSA-N Copy
• CAS Registry Number: 1333-74-0
• 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.
• Isotopologues:
  • tritium
  • deuterium hydride
  • Deuterium
• Other names: Dihydrogen; o-Hydrogen; p-Hydrogen; Molecular hydrogen; H2; UN 1049; UN 1966
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase ion energetics data
  • Ion clustering data
  • Mass spectrum (electron ionization)
  • References
  • Notes
• Other data available:
  • Gas phase thermochemistry data
  • Phase change data
  • Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 100, reactions 101 to 150, reactions 151 to 200, reactions 201 to 250, reactions 251 to 300, reactions 301 to 350, reactions 351 to 400, reactions 401 to 450, reactions 451 to 500, reactions 501 to 550, reactions 551 to 600, reactions 601 to 621
  • Henry's Law data
  • Constants of diatomic molecules
  • Fluid Properties
• Data at other public NIST sites:
  • Electron-Impact Ionization Cross Sections (on physics web site)
  • Gas Phase Kinetics Database
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Gas phase ion energetics data

Go To: Top, Ion clustering 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
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 H₂⁺ (ion structure unspecified)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

 +  =

By formula: H^- + H⁺ = H₂

Ion clustering data

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

Data compiled by: 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. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

Ar⁺ +  = (Ar⁺ • )

By formula: Ar⁺ + H₂ = (Ar⁺ • H₂)

 +  = ( • )

By formula: CHO⁺ + H₂ = (CHO⁺ • H₂)

CH₅⁺ +  = (CH₅⁺ • )

By formula: CH₅⁺ + H₂ = (CH₅⁺ • H₂)

(CH₅⁺ • ) +  = (CH₅⁺ • 2)

By formula: (CH₅⁺ • H₂) + H₂ = (CH₅⁺ • 2H₂)

(CH₅⁺ • 2) +  = (CH₅⁺ • 3)

By formula: (CH₅⁺ • 2H₂) + H₂ = (CH₅⁺ • 3H₂)

(CH₅⁺ • 3) +  = (CH₅⁺ • 4)

By formula: (CH₅⁺ • 3H₂) + H₂ = (CH₅⁺ • 4H₂)

C₃H₇⁺ +  = (C₃H₇⁺ • )

By formula: C₃H₇⁺ + H₂ = (C₃H₇⁺ • H₂)

Free energy of reaction

( • ) +  = ( •  • )

By formula: (Co⁺ • CH₄) + H₂ = (Co⁺ • H₂ • CH₄)

Enthalpy of reaction

( • ) +  = ( •  • )

By formula: (Co⁺ • H₂O) + H₂ = (Co⁺ • H₂ • H₂O)

Enthalpy of reaction

 +  = ( • )

By formula: Co⁺ + H₂ = (Co⁺ • H₂)

Enthalpy of reaction

( • ) +  = ( • 2)

By formula: (Co⁺ • H₂) + H₂ = (Co⁺ • 2H₂)

( • 2) +  = ( • 3)

By formula: (Co⁺ • 2H₂) + H₂ = (Co⁺ • 3H₂)

( • 3) +  = ( • 4)

By formula: (Co⁺ • 3H₂) + H₂ = (Co⁺ • 4H₂)

( • 4) +  = ( • 5)

By formula: (Co⁺ • 4H₂) + H₂ = (Co⁺ • 5H₂)

( • 5) +  = ( • 6)

By formula: (Co⁺ • 5H₂) + H₂ = (Co⁺ • 6H₂)

( • 6) +  = ( • 7)

By formula: (Co⁺ • 6H₂) + H₂ = (Co⁺ • 7H₂)

 +  = ( • )

By formula: Fe⁺ + H₂ = (Fe⁺ • H₂)

( • ) +  = ( • 2)

By formula: (Fe⁺ • H₂) + H₂ = (Fe⁺ • 2H₂)

( • 2) +  = ( • 3)

By formula: (Fe⁺ • 2H₂) + H₂ = (Fe⁺ • 3H₂)

( • 3) +  = ( • 4)

By formula: (Fe⁺ • 3H₂) + H₂ = (Fe⁺ • 4H₂)

( • 4) +  = ( • 5)

By formula: (Fe⁺ • 4H₂) + H₂ = (Fe⁺ • 5H₂)

( • 5) +  = ( • 6)

By formula: (Fe⁺ • 5H₂) + H₂ = (Fe⁺ • 6H₂)

HN₂⁺ +  = (HN₂⁺ • )

By formula: HN₂⁺ + H₂ = (HN₂⁺ • H₂)

(HN₂⁺ • ) +  = (HN₂⁺ • 2)

By formula: (HN₂⁺ • H₂) + H₂ = (HN₂⁺ • 2H₂)

 +  = ( • )

By formula: HO^- + H₂ = (HO^- • H₂)

HO₂⁺ +  = (HO₂⁺ • )

By formula: HO₂⁺ + H₂ = (HO₂⁺ • H₂)

(HO₂⁺ • ) +  = (HO₂⁺ •  • )

By formula: (HO₂⁺ • O₂) + H₂ = (HO₂⁺ • H₂ • O₂)

H₃⁺ +  = (H₃⁺ • )

By formula: H₃⁺ + H₂ = (H₃⁺ • H₂)

(H₃⁺ • ) +  = (H₃⁺ • 2)

By formula: (H₃⁺ • H₂) + H₂ = (H₃⁺ • 2H₂)

(H₃⁺ • 2) +  = (H₃⁺ • 3)

By formula: (H₃⁺ • 2H₂) + H₂ = (H₃⁺ • 3H₂)

(H₃⁺ • 3) +  = (H₃⁺ • 4)

By formula: (H₃⁺ • 3H₂) + H₂ = (H₃⁺ • 4H₂)

(H₃⁺ • 4) +  = (H₃⁺ • 5)

By formula: (H₃⁺ • 4H₂) + H₂ = (H₃⁺ • 5H₂)

(H₃⁺ • 5) +  = (H₃⁺ • 6)

By formula: (H₃⁺ • 5H₂) + H₂ = (H₃⁺ • 6H₂)

(H₃⁺ • 6) +  = (H₃⁺ • 7)

By formula: (H₃⁺ • 6H₂) + H₂ = (H₃⁺ • 7H₂)

(H₃⁺ • 7) +  = (H₃⁺ • 8)

By formula: (H₃⁺ • 7H₂) + H₂ = (H₃⁺ • 8H₂)

(H₃⁺ • 8) +  = (H₃⁺ • 9)

By formula: (H₃⁺ • 8H₂) + H₂ = (H₃⁺ • 9H₂)

 +  = ( • )

By formula: H₃O⁺ + H₂ = (H₃O⁺ • H₂)

 +  = ( • )

By formula: K⁺ + H₂ = (K⁺ • H₂)

( • ) +  = ( • 2)

By formula: (K⁺ • H₂) + H₂ = (K⁺ • 2H₂)

 +  = ( • )

By formula: Li⁺ + H₂ = (Li⁺ • H₂)

 +  = ( • )

By formula: Na⁺ + H₂ = (Na⁺ • H₂)

( • ) +  = ( • 2)

By formula: (Na⁺ • H₂) + H₂ = (Na⁺ • 2H₂)

Mass spectrum (electron ionization)

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

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Additional Data

References

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

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]

Shiner, Gilligan, et al., 1993
Shiner, D.; Gilligan, J.M.; Cook, B.M.; Lichten, W., H₂, D₂, and HD ionization potentials by accurate calibration of several iodine lines, Phys. Rev. A, 1993, 47, 4042. [all data]

McCormack, Gilligan, et al., 1989
McCormack, E.; Gilligan, J.M.; Cornaggia, C.; Eyler, E.E., Measurement of high Rydberg states and the ionization potential of H₂, Phys. Rev. A, 1989, 39, 2260. [all data]

Glab and Hessler, 1987
Glab, W.L.; Hessler, J.P., Multiphoton excitation of high singlet np Rydberg states of molecular hydrogen: Spectroscopy and dynamics, Phys. Rev. A, 1987, 35, 2102. [all data]

Eyler, Short, et al., 1986
Eyler, E.E.; Short, R.C.; Pipkin, F.M., Precision spectroscopy of the nf triplet Rydberg states of H₂ and determination of the triplet ionization potential, Phys. Rev. Lett., 1986, 56, 2602. [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]

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]

Bieri, Schmelzer, et al., 1980
Bieri, G.; Schmelzer, A.; Asbrink, L.; Jonsson, M., Fluorine and the fluoroderivatives of acetylene and diacetylene studied by 30.4 nm He(II) photoelectron spectroscopy, Chem. Phys., 1980, 49, 213. [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]

Farber and Srivastava, 1977
Farber, M.; Srivastava, R.D., Mass spectrometric determination of the heats of formation of the silane fluorides, Chem. Phys. Lett., 1977, 51, 307. [all data]

Rabalais, Debies, et al., 1974
Rabalais, J.W.; Debies, T.P.; Berkosky, J.L.; Huang, J.-T.J.; Ellison, F.O., Calculated photoionization cross sections relative experimental photoionization intensities for a selection of small molecules, J. Chem. Phys., 1974, 61, 516. [all data]

Lee and Rabalais, 1974
Lee, T.H.; Rabalais, J.W., Vibrational transition probabilities in photoelectron spectra, J. Chem. Phys., 1974, 61, 2747. [all data]

Herzberg and Jungen, 1972
Herzberg, G.; Jungen, Ch., Rydberg series and ionization potential of the H₂ molecule, J. Mol. Spectrosc., 1972, 41, 425. [all data]

Takezawa, 1970
Takezawa, S., Absorption spectrum of H₂ in the vacuum-uv region. II. Rydberg series converging to the first six vibrational levels of the H₂⁺ ground state, J. Chem. Phys., 1970, 52, 5793. [all data]

Asbrink, 1970
Asbrink, L., The photoelectron spectrum of H₂, Chem. Phys. Lett., 1970, 7, 549. [all data]

Lossing and Semeluk, 1969
Lossing, F.P.; Semeluk, G.P., Threshold ionization efficiency curves for monoenergetic electron impact on H₂, D₂, CH₄ and CD₄, Intern. J. Mass Spectrom. Ion Phys., 1969, 2, 408. [all data]

Herzberg, 1969
Herzberg, G., Dissociation energy and ionization potential of molecular hydrogen, Phys. Rev. Letters, 1969, 23, 1081. [all data]

Villarejo, 1968
Villarejo, D., Measurement of threshold electrons in the photoionization of H₂ and D₂, J. Chem. Phys., 1968, 48, 4014. [all data]

Collin and Natalis, 1968
Collin, J.E.; Natalis, P., Vibrational and electronic ionic states of nitric oxide. An accurate method for measuring ionization potentials by photoelectron spectroscopy, Intern. J. Mass Spectrom. Ion Phys., 1968, 1, 483. [all data]

Cermak, 1968
Cermak, V., Penning ionization electron spectroscopy. I. Determination of ionization potentials of polyatomic molecules, Collection Czech. Chem. Commun., 1968, 33, 2739. [all data]

Kerwin, Marmet, et al., 1963
Kerwin, L.; Marmet, P.; Clarke, E.M., Recent work with the electrostatic electron selector, Advan. Mass Spectrom., 1963, 2, 522. [all data]

Beutler and Junger, 1936
Beutler, H.; Junger, H.-O., Uber das Absorptionsspektrum des Wasserstoffs. III. Die Autoionisierung im Term 3pπ 1u des H₂ und ihre Auswahlgesetze. Bestimmung der lonisierungsenergie des H₂, Z. Physik, 1936, 100, 80. [all data]

Weitzel, Mahnert, et al., 1994
Weitzel, K.-M.; Mahnert, J.; Penno, M., ZEKE-PEPICO investigations of dissociation energies in ionic reactions, Chem. Phys. Lett., 1994, 224, 371. [all data]

Crowe and McConkey, 1973
Crowe, A.; McConkey, J.W., Dissociative ionization by electron impact. I. Protons from H₂, J. Phys. B:, 1973, 6, 2088. [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]

Curran, Laboratories
Curran, R.K., Negative ion formation in various gases at pressures up to .5 mm of Hg, Scientific Paper 62-908-113-P7, Westinghouse Research, Laboratories, Pittsburgh, 1962. [all data]

Shiell, Hu, et al., 2000
Shiell, R.C.; Hu, X.K.; Hu, Q.C.J.; Hepburn, J.W., Threshold Ion-pair Production spectroscopy (TIPPS) of H2 and D2, Faraday Disc. Chem. Soc., 2000, 115, 331, https://doi.org/10.1039/a909428h . [all data]

Pratt, McCormack, et al., 1992
Pratt, S.T.; McCormack, E.F.; Dehmer, J.L.; Dehmer, P.M., Field-Induced Ion-Pair Formation in Molecular Hydrogen, Phys. Rev. Lett., 1992, 68, 5, 584, https://doi.org/10.1103/PhysRevLett.68.584 . [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]

Lykke, Murray, et al., 1991
Lykke, K.R.; Murray, K.K.; Lineberger, W.C., Threshold Photodetachment of H-, Phys. Rev. A, 1991, 43, 11, 6104, https://doi.org/10.1103/PhysRevA.43.6104 . [all data]

Shul, Passarella, et al., 1987
Shul, R.J.; Passarella, R.; Upshulte, B.L.; Keesee, R.G.; Castleman, A.W., Thermal Energy Reactions Invoving Ar+ Monomer and Dimer with N2, H2, Xe, and Kr, J. Chem. Phys., 1987, 86, 8, 4446, https://doi.org/10.1063/1.452718 . [all data]

Dehmer and Pratt, 1982
Dehmer, P.M.; Pratt, S.T., Photoionization of ArKr, ArXe, and KrXe and bond dissociation energies of the rare gas dimer ions, J. Chem. Phys., 1982, 77, 4804. [all data]

Hiraoka and Kebarle, 1975
Hiraoka, K.; Kebarle, P., Stability and Structure of H3CO+ Formed from COH+ + H2 at Low Temperature, J. Chem. Phys., 1975, 63, 4, 1688, https://doi.org/10.1063/1.431499 . [all data]

Hiraoka, Kudaka, et al., 1991
Hiraoka, K.; Kudaka, I.; Yamabe, S., Gas-Phase Solvation of CH5+ with H2, Chem. Phys. Lett., 1991, 184, 4, 271, https://doi.org/10.1016/0009-2614(91)85122-D . [all data]

Hiraoka and Kebarle, 1976
Hiraoka, K.; Kebarle, P., Stabilities and Energetics of Pentacoordinated Carbonium Ions. The Isomeric C2H7+ Ions and Some Higher Analogues: C3H9+ and C4H11+, J. Am. Chem. Soc., 1976, 98, 20, 6119, https://doi.org/10.1021/ja00436a009 . [all data]

Kemper, Bushnell, et al., 1993
Kemper, P.R.; Bushnell, J.; Von Koppen, P.; Bowers, M.T., Binding Energies of Co+(H2/CH4/C2H6)1,2,3 Clusters, J. Phys. Chem., 1993, 97, 9, 1810, https://doi.org/10.1021/j100111a016 . [all data]

Kemper, Bushnell, et al., 1993, 2
Kemper, P.R.; Bushnell, J.; Von Helden, G.; Bowers, M.T., Co+(H2)n Clusters: Binding Energies and Molecular Parameters, J. Chem Phys., 1993, 97, 1, 52, https://doi.org/10.1021/j100103a012 . [all data]

Haynes and Armentrout, 1996
Haynes, C.L.; Armentrout, P.B., Guided Ion Beam Determination of the Co+ - H2 Bond Dissociation energy, Chem Phys. Let., 1996, 249, 1-2, 64, https://doi.org/10.1016/0009-2614(95)01337-7 . [all data]

Bushnell, Kemper, et al., 1995
Bushnell, J.E.; Kemper, P.R.; Bowers, M.T., Factors Affecting sigma Bond Activation in Simple Systems; Measurement of Experimental Binding energies of Fe+(H2)1-6 Clusters, J. Phys. Chem., 1995, 99, 42, 15602, https://doi.org/10.1021/j100042a040 . [all data]

Hiraoka, Saluja, et al., 1979
Hiraoka, K.; Saluja, P.P.S.; Kebarle, P., Stabilities of Complexes (N2)nH+, (CO)nH+ and (O2)nH+ for n = 1 to 7 Based on Gas Phase Ion Equilibrium Measurements, Can. J. Chem., 1979, 57, 16, 2159, https://doi.org/10.1139/v79-346 . [all data]

Paulson and Henchman, 1984
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Hiraoka, 1987
Hiraoka, K., A Determination of the Stabilities of H3+(H2)n with n=1-9 from Measurements of the gas-Phase Ion Equilibria H3+(H2)n-1 + H2 = H3+(H2)n, J. Chem. Phys., 1987, 87, 7, 4048, https://doi.org/10.1063/1.452909 . [all data]

Beuhler, Ehrenson, et al., 1983
Beuhler, R.J.; Ehrenson, S.; Friedman, L., Hydrogen Cluster Ion Equilibria, J. Chem. Phys., 1983, 79, 12, 5982, https://doi.org/10.1063/1.445781 . [all data]

Hiraoka and Kebarle, 1975, 2
Hiraoka, K.; Kebarle, P., A Determination of the Stabilities of H5+, H7+, H9+, and H11+ from Measurement of the Gas Phase Ion Equilibria Hn+ + H2 = H(n + 2)+ (n = 3, 5, 7, 9), J. Chem. Phys., 1975, 62, 6, 2267, https://doi.org/10.1063/1.430751 . [all data]

Bennett and Field, 1972
Bennett, S.L.; Field, F.H., Reversible Reactions of Gaseous Ions. VII. The Hydrogen System, J. Am. Chem. Soc., 1972, 94, 25, 8669, https://doi.org/10.1021/ja00780a003 . [all data]

Okumura, Yeh, et al., 1990
Okumura, M.; Yeh, L.I.; Myers, J.D.; Lee, Y.T., Infrared Spectra of the Solvated Hydronium Ion: Vibrational Predissociation Spectroscopy of Mass-Selected H3O+.(H2O)n.(H2)m, J. Phys. Chem., 1990, 94, 9, 3416, https://doi.org/10.1021/j100372a014 . [all data]

Bushnell, Kemper, et al., 1994
Bushnell, J.E.; Kemper, P.R.; Bowers, M.T., Na+/K+(H2)1,2 clusters: experiment, J. Phys. Chem., 1994, 98, 8, 2044, https://doi.org/10.1021/j100059a011 . [all data]

Wu, 1979
Wu, C.H., Binding Energies of LiH2 and LiH2+ and the Ionization Potential of LiH2, J. Chem. Phys., 1979, 71, 2, 783, https://doi.org/10.1063/1.438367 . [all data]

Notes

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

• Symbols used in this document:
  

  AE	Appearance energy
  IE (evaluated)	Recommended ionization energy
  T	Temperature
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔrS°	Entropy of reaction at standard conditions

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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