Selected ATcT [1, 2] enthalpy of formation based on version 1.156 of the Thermochemical Network [3]

This version of ATcT results[3] was generated by additional expansion of version 1.148 to include species relevant to a recent study of the oxidation of ethylene [4] as well as new measurements that led to refining the thermochemistry of CF and SiF and their cations [5].

Dihelium anion

Formula: [He2]- (g, quartet 4Pig)

CAS RN: 90188-47-9

ATcT ID: 90188-47-9*1

SMILES: [He][He-]

InChI: InChI=1S/He2/c1-2/q-1

InChIKey: TUONMHFMKUTRCM-UHFFFAOYSA-N

Hills Formula: He2-

2D Image:

Aliases: [He2]-; Dihelium anion; Dihelium ion (1-); Diatomic helium anion; Diatomic helium ion (1-); Helium dimer anion; Helium dimer ion (1-); Molecular helium anion; Molecular helium ion (1-)

Relative Molecular Mass: 8.0057526 ± 0.0000040

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
1714.9	1711.2	± 1.9	kJ/mol

3D Image of [He2]- (g, quartet 4Pig)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of [He2]- (g, quartet 4Pig)

The 7 contributors listed below account for 92.4% of the provenance of Δ_fH° of [He2]- (g, quartet 4Pig).

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
42.0	9061.1	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.175 ± 0.030 eV	Kvale 1986
15.3	9063.1	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -142978 ± 400 cm-1	Pluta 1989, est unc
15.1	9061.2	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.212 ± 0.050 eV	Pluta 1989, est unc
5.9	9061.4	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.182 ± 0.080 eV	Michels 1986, est unc
5.8	9063.3	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -143465 ± 650 cm-1	Michels 1986, est unc
4.3	9068.2	[He2]- (g, quartet 4Pig) → He (g, triplet) + He (g)	Δ_rH°(0 K) = 1.954 ± 0.080 (×1.164) eV	Michels 1986, est unc
3.8	9063.2	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -143058 ± 800 cm-1	Michels 1984, est unc

Most Influential reactions involving [He2]- (g, quartet 4Pig)

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
0.420	9061.1	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.175 ± 0.030 eV	Kvale 1986
0.153	9063.1	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -142978 ± 400 cm-1	Pluta 1989, est unc
0.151	9061.2	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.212 ± 0.050 eV	Pluta 1989, est unc
0.059	9061.4	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.182 ± 0.080 eV	Michels 1986, est unc
0.058	9063.3	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -143465 ± 650 cm-1	Michels 1986, est unc
0.043	9068.2	[He2]- (g, quartet 4Pig) → He (g, triplet) + He (g)	Δ_rH°(0 K) = 1.954 ± 0.080 (×1.164) eV	Michels 1986, est unc
0.038	9063.2	[He2]- (g, quartet 4Pig) → 2 He (g)	Δ_rH°(0 K) = -143058 ± 800 cm-1	Michels 1984, est unc
0.037	9068.1	[He2]- (g, quartet 4Pig) → He (g, triplet) + He (g)	Δ_rH°(0 K) = 2.005 ± 0.100 eV	Michels 1984, est unc
0.037	9061.3	[He2]- (g, quartet 4Pig) → He2 (g, triplet)	Δ_rH°(0 K) = 0.233 ± 0.100 eV	Michels 1984, est unc

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. 1.156 of the Thermochemical Network (2024); available at ATcT.anl.gov

4 N. A. Seifert, B. Ruscic, R. Sivaramakrishnan, and K. Prozument,
The C2H4O Isomers in the Oxidation of Ethylene
J. Mol. Spectrosc. 398, 111847/1-8 (2023) [DOI: 10.1016/j.jms.2023.111847]

5 U. Jacovella, B. Ruscic, N. L. Chen, H.-L. Le, S. Boyé-Péronne, S. Hartweg, M. Roy-Chowdhury, G. A. Garcia, J.-C. Loison, and B. Gans,
Refining Thermochemical Properties of CF, SiF, and Their Cations by Combining Photoelectron Spectroscopy, Quantum Chemical Calculations, and the Active Thermochemical Tables Approach
Phys. Chem. Chem. Phys. 25, 30838-30847 (2023) [DOI: 10.1039/D3CP04244H]

6 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]

7 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 [6] and Ruscic and Bross[7]).
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.