Selected ATcT [1, 2] enthalpy of formation based on version 1.124 of the Thermochemical Network [3]

This version of ATcT results was generated by additional expansion of version 1.122x [4] to include additional information relevant to the study of thermophysical and thermochemical properties of CH2 and CH3 using nonrigid rotor anharmonic oscillator (NRRAO) partition functions [5], the development and benchmarking of a state-of-the-art computational approach that aims to reproduce total atomization energies of small molecules within 10–15 cm^-1 [6], as well as the study of the reversible reaction C₂H₃ + H₂ ⇌ C₂H₄ + H ⇌ C₂H₅ [7]

Helium

Formula: He (g, triplet)

CAS RN: 7440-59-7

ATcT ID: 7440-59-7*1

SMILES: [He]

InChI: InChI=1S/He

InChIKey: SWQJXJOGLNCZEY-UHFFFAOYSA-N

Hills Formula: He1

2D Image:

Aliases: He; Helium; Helium atom; Atomic helium

Relative Molecular Mass: 4.0026020 ± 0.0000020

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
1912.302	1912.302	± 0.000	kJ/mol

3D Image of He (g, triplet)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of He (g, triplet)

The 3 contributors listed below account for 99.9% of the provenance of Δ_fH° of He (g, triplet).

Please note: The list is limited to 20 most important contributors or, if less, a number sufficient to account for 90% of the provenance. The Reference acts as a further link to the relevant references and notes for the measurement. The Measured Quantity is normaly given in the original units; in cases where we have reinterpreted the original measurement, the listed value may differ from that given by the authors. The quoted uncertainty is the a priori uncertainty used as input when constructing the initial Thermochemical Network, and corresponds either to the value proposed by the original authors or to our estimate; if an additional multiplier is given in parentheses immediately after the prior uncertainty, it corresponds to the factor by which the prior uncertainty needed to be multiplied during the ATcT analysis in order to make that particular measurement consistent with the prevailing knowledge contained in the Thermochemical Network.

Contribution (%)	TN ID	Reaction	Measured Quantity	Reference
66.6	7988.1	He (g, singlet) → He (g)	Δ_rH°(0 K) = 0 ± 0 cm-1	triv, NIST Atomic Web
16.6	7989.2	He (g, singlet) → He (g, triplet)	Δ_rH°(0 K) = 159855.9745 ± 0.0005 cm-1	Sansonetti 2005, est unc
16.6	7989.1	He (g, singlet) → He (g, triplet)	Δ_rH°(0 K) = 159855.9743297 ± 0.0000020 cm-1	NIST Atomic Web, Morton 2006

Top 10 species with enthalpies of formation correlated to the Δ_fH° of He (g, triplet)

Please note: The correlation coefficients are obtained by renormalizing the off-diagonal elements of the covariance matrix by the corresponding variances.
The correlation coefficient is a number from -1 to 1, with 1 representing perfectly correlated species, -1 representing perfectly anti-correlated species, and 0 representing perfectly uncorrelated species.

Correlation Coefficent (%)	Species Name	Formula	Image	Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units	Relative Molecular Mass	ATcT ID
81.6	Helium	He (g, singlet)		0.000	0.000	± 0.000	kJ/mol	4.0026020 ± 0.0000020	7440-59-7*2
64.4	Helium anion	He- (g, 1s.2s.2p 4P)		1904.822	1904.822	± 0.000	kJ/mol	4.0031506 ± 0.0000020	14452-58-5*3

Most Influential reactions involving He (g, triplet)

Please note: The list, which is based on a hat (projection) matrix analysis, is limited to no more than 20 largest influences.

Influence Coefficient	TN ID	Reaction	Measured Quantity	Reference
0.999	7996.1	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.07752848 ± 0.00000018 eV	Wang 2014, note unc
0.500	7989.1	He (g, singlet) → He (g, triplet)	Δ_rH°(0 K) = 159855.9743297 ± 0.0000020 cm-1	NIST Atomic Web, Morton 2006
0.500	7989.2	He (g, singlet) → He (g, triplet)	Δ_rH°(0 K) = 159855.9745 ± 0.0005 cm-1	Sansonetti 2005, est unc
0.108	7997.1	He- (g, 2p3 4S3/2) → He (g, triplet)	Δ_rH°(0 K) = -39.5132 ± 0.010 eV	Turbiner 2013, Bylicki 1996, est unc, Tech 1971
0.043	8007.2	[He2]- (g, quartet 4Pig) → He (g, triplet) + He (g)	Δ_rH°(0 K) = 1.954 ± 0.080 (×1.164) eV	Michels 1986, est unc
0.037	8007.1	[He2]- (g, quartet 4Pig) → He (g, triplet) + He (g)	Δ_rH°(0 K) = 2.005 ± 0.100 eV	Michels 1984, est unc
0.017	7997.2	He- (g, 2p3 4S3/2) → He (g, triplet)	Δ_rH°(0 K) = -39.517 ± 0.025 eV	Turbiner 2013, Bylicki 1996, Trabert 1992, Walter 1994, Tech 1971
0.004	7997.4	He- (g, 2p3 4S3/2) → He (g, triplet)	Δ_rH°(0 K) = -39.526 ± 0.050 eV	Chung 1979, est unc, Tech 1971
0.004	7997.3	He- (g, 2p3 4S3/2) → He (g, triplet)	Δ_rH°(0 K) = -39.537 ± 0.050 eV	Nicolaides 1981, est unc, Tech 1971
0.000	7996.3	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.077516 ± 0.000012 (×1.044) eV	Kristensen 1997a, note unc
0.000	7996.2	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.077518 ± 0.000022 eV	Kristensen 1997a, note unc
0.000	7990.1	He (g, triplet) → He+ (g)	Δ_rH°(0 K) = 38454.8274 ± 0.2 cm-1	Accad 1971, est unc
0.000	7996.4	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.07767 ± 0.00012 (×1.189) eV	Walter 1994
0.000	7996.7	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.07751 ± 0.0008 eV	Bunge 1984, Turbiner 2013, Bylicki 1996, note unc
0.000	7996.5	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.0775 ± 0.0008 eV	Peterson 1985
0.000	7996.6	He- (g, 1s.2s.2p 4P) → He (g, triplet)	Δ_rH°(0 K) = 0.0774 ± 0.003 eV	Bunge 1979

References

1		B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 108, 9979-9997 (2004) [DOI: 10.1021/jp047912y]
2		B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active Thermochemical Tables: Thermochemistry for the 21^st Century. J. Phys. Conf. Ser. 16, 561-570 (2005) [DOI: 10.1088/1742-6596/16/1/078]
3		B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) values based on ver. 1.124 of the Thermochemical Network, Argonne National Laboratory, Lemont, Illinois 2022; available at ATcT.anl.gov [DOI: 10.17038/CSE/1885923]
4		Y. Ren, L. Zhou, A. Mellouki, V. Daële, M. Idir, S. S. Brown, B. Ruscic, Robert S. Paton, M. R. McGillen, and A. R. Ravishankara, Reactions of NO3 with Aromatic Aldehydes: Gas-Phase Kinetics and Insights into the Mechanism of the Reaction. Atmos. Chem. Phys. 21, 13537-13551 (2021) [DOI: 10.5194/acp2021-228]
5		B. Ruscic and D. H. Bross, Active Thermochemical Tables: The Thermophysical and Thermochemical Properties of Methyl, CH3, and Methylene, CH2, Corrected for Nonrigid Rotor and Anharmonic Oscillator Effects. Mol. Phys. e1969046 (2021) [DOI: 10.1080/00268976.2021.1969046]
6		J. H. Thorpe, J. L. Kilburn, D. Feller, P. B. Changala, D. H. Bross, B. Ruscic, and J. F. Stanton, Elaborated Thermochemical Treatment of HF, CO, N2, and H2O: Insight into HEAT and Its Extensions J. Chem. Phys. 155, 184109 (2021) [DOI: 10.1063/5.0069322]
7		T. L. Nguyen, D. H. Bross, B. Ruscic, G. B. Ellison, and J. F. Stanton, Mechanism, Thermochemistry, and Kinetics of the Reversible Reactions: C2H3 + H2 ⇌ C2H4 + H ⇌ C2H5. Faraday Discuss. , (Advance Article) (2022) [DOI: 10.1039/D1FD00124H]
8		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014) [DOI: 10.1002/qua.24605]
9		B. Ruscic and D. H. Bross, Thermochemistry Computer Aided Chem. Eng. 45, 3-114 (2019) [DOI: 10.1016/B978-0-444-64087-1.00001-2]

Formula

The aggregate state is given in parentheses following the formula, such as: g - gas-phase, cr - crystal, l - liquid, etc.

Uncertainties

The listed uncertainties correspond to estimated 95% confidence limits, as customary in thermochemistry (see, for example, Ruscic [8,9]).
Note that an uncertainty of ± 0.000 kJ/mol indicates that the estimated uncertainty is < ± 0.000₅ kJ/mol.

Website Functionality Credits

The reorganization of the website was developed and implemented by David H. Bross (ANL).
The find function is based on the complete Species Dictionary entries for the appropriate version of the ATcT TN.
The molecule images are rendered by Indigo-depict.
The XYZ renderings are based on Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/.

Acknowledgement

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Contract No. DE-AC02-06CH11357.