Lithium dimer

Formula: Li₂
Molecular weight: 13.882
IUPAC Standard InChI: InChI=1S/2Li
IUPAC Standard InChIKey: SMBQBQBNOXIFSF-UHFFFAOYSA-N
CAS Registry Number: 14452-59-6
Chemical structure:
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Other data available:
- Gas phase thermochemistry data
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Gas phase ion energetics data

Go To: Top, Constants of diatomic molecules, References, Notes

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

Data compiled as indicated in comments:
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

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	5.1127 ± 0.0003	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	277.7	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	270.82	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
4.73 ± 0.05	PI	Dugourd, Rayane, et al., 1992	LL
5.1127 ± 0.0003	S	McGeogh and Schlier, 1983	LBLHLM
5.14	PI	Eisel and Demtroder, 1982	LBLHLM
5.0 ± 0.3	EI	N/A	LLK
5.00	EVAL	Huber and Herzberg, 1979	LLK
5.174 ± 0.013	PI	Mathur, Rothe, et al., 1978	LLK
5.0	EI	Zmbov, Wu, et al., 1977	LLK
4.9 ± 0.1	EI	N/A	LLK
4.9 ± 0.1	EI	Ihle and Wu, 1975	LLK
4.9 ± 0.1	EI	Emel'yanov, Peredvigina, et al., 1971	LLK
5.2 ± 0.1	PI	Foster, Leckenby, et al., 1969	RDSH
5.0 ± 0.1	S	Velasco, 1960	RDSH

Constants of diatomic molecules

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

Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through March, 1977

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for ⁷Li₂
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
Fragments of other absorption band systems in the ultraviiolet. REFS 5
D ¹Π_u	(34518) 1	[201.68] 1 Z			0.4628 2	0.0073		11.4E-6		3.222	D ← X R	34443.58 1 Z
D ¹Π_u	↳Barrow, Travis, et al., 1960; Mercier, Rico, et al., 1969
C ¹Π_u	30550.6	237.9 Z	3.35	0.064	0.5075 3	0.0097₃ 4	0.00015₄	9E-6		3.077	C ← X R	30493.6 Z
C ¹Π_u	↳Vance and Huffman, 1935; Sinha, 1948; Barrow, Travis, et al., 1960; Velasco, 1960; Rico, 1969
B ¹Π_u	20436.01	270.12 Z	2.67₃ 5	-0.082₅	0.5577 6 3	0.0085	-0.00014	9.45E-6	0.14E-6	2.935	B ↔ X 7 R	20395.32 Z
B ¹Π_u	↳missing citation; Loomis and Nusbaum, 1931; McKellar, 1933; Velasco, Ottinger, et al., 1969; Ottinger, Velasco, et al., 1970; Velasco, Ruano, et al., 1970; Ottinger and Poppe, 1971
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
A ¹Σ_u⁺	14068.35	255.47 Z	1.58₂	.002₅	0.4975₀ 3	0.0054₀		7.54E-6 8		3.107₉	A ← X 7 R	14020.63 Z
A ¹Σ_u⁺	↳Almy and Irwin, 1936; missing citation
a ³Σ_u⁺	Not observed; predicted potential minimum of ~300 cm^-1 at 4.3Å Kutzelnigg, Staemmler, et al., 1972.
X ¹Σ_g⁺	0	351.43 Z	2.610 9	0.00295	0.67264 3	0.00704 10	-0.00004	9.87E-6 11		2.6729 12
X ¹Σ_g⁺	↳Logan, Cote, et al., 1952; Brooks, Anderson, et al., 1963

Notes

Vibrational numbering uncertain.

Rotational constants from Q branches only; see also 1.

missing note

Rotational constants from Q branches only; Velasco, 1960 gives B(R,P) - B(Q) = 0.0024 Velasco, 1960.

Vibrational constants recalculated from band origins (v' = 0....4) of Velasco, Ruano, et al., 1970. Slightly different constants in Loomis and Nusbaum, 1931, from a low-resolution magnetic rotation spectrum including much higher vibrational levels. The B ¹Π_u state has a potential maximum of ~ 0.09 eV King and Van Vleck, 1939, Velasco, Ottinger, et al., 1969, Olson and Konowalow, 1976; the theoretical calculations of Kahn, Dunning, et al., 1977 predict a barrier of 0.0724 eV at 5.61 .

Slightly different constants in Velasco, Ennen, et al., 1973; Λ-type doubling Δv_ef ~ +0.00016J(J+1).

The B-X and A-X systems of ⁶Li₂ have been analyzed by Velasco and Morales, 1973 and Velasco and Rivero, 1972, respectively.

H_e = +1.23E-10.

w_ez_e = -0.000636; from the B→X fluorescence spectrum Velasco, Ottinger, et al., 1969, including levels from v=0 to 18.

(v=0...4) McKellar and Jenkins, 1939. For v>>10 B_v and D_v are better represented by B_v = B₁₀ - 0.0077(v - 10) - 0.00016(v - 10)² and D_v = D₁₀ + 0.22E-6(v-10) Velasco, Ottinger, et al., 1969.

H_e = +1.54E-10. See also 10.

Mol. beam magn. Reson. 16

Value recommended by Stwalley, 1976. Extrapolation of the ground state vibrational levels, taking into account the contribution due to long-range forces, gives 8473 cm^-1 [1.051 eV, see Stwalley, 1976]. The latest thermochemical value [mass spectrometry missing citation] is 1.11 eV; see also Lewis, 1931, who obtained 1.03 eV using a molecular beam method.

Average of a photoionization Foster, Leckenby, et al., 1969, and electron impact missing citation, appearance potential (5.15 and 4.86 eV, respectively). The Rydberg series B,C,D... extrapolate to 4.99 eV Velasco, 1973.

RKR potential curves Krupenie, Mason, et al., 1963.

g_J = 0.1079₇ μ_N Brooks, Anderson, et al., 1963. Li nuclear electric quadrupole coupling constant Logan, Cote, et al., 1952.

D₀⁰(Li₂) + I.P.(Li) - I. P.(Li₂).

From D₀⁰(Li₂) and the electron affinities of Li₂ and Li.

Theoretical electron affinity of Li₂ from an ab initio calculation by Dixon, Gole, et al., 1977. A value of 0.90 eV was computed earlier by Andersen and Simons, 1976, but see Dixon, Gole, et al., 1977.

References

Go To: Top, Gas phase ion energetics data, Constants of diatomic molecules, Notes

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]

Dugourd, Rayane, et al., 1992
Dugourd, P.; Rayane, D.; Labastie, P.; Vezin, B.; Chevaleyre, J.; Broyer, M., Measurements of lithium cluster ionization potentials, Chem. Phys. Lett., 1992, 197, 433. [all data]

McGeogh and Schlier, 1983
McGeogh, M.W.; Schlier, R.E., Autoionizing Rydberg states of the Li₂ molecule: Molecular constants for Li₂⁺, Chem. Phys. Lett., 1983, 99, 347. [all data]

Eisel and Demtroder, 1982
Eisel, D.; Demtroder, W., Accurate ionization potential of Li₂ from resonant two-photon ionization, Chem. Phys. Lett., 1982, 88, 481. [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]

Mathur, Rothe, et al., 1978
Mathur, B.P.; Rothe, E.W.; Reck, G.P.; Lightman, A.J., Two-photon ionization of Li₂: isotopic separation and determination of IP(Li₂) and D_e (Li₂⁺), Chem. Phys. Lett., 1978, 56, 336. [all data]

Zmbov, Wu, et al., 1977
Zmbov, K.F.; Wu, C.H.; Ihle, H.R., A mass spectrometric study of heteronuclear diatomic alkali metal molecules. Dissociation energies ionization potentials of NaLi, KLi, NaK, J. Chem. Phys., 1977, 67, 4603. [all data]

Ihle and Wu, 1975
Ihle, H.R.; Wu, C.H., Mass spectrometric determination of the ionization potential and dissociation energy of LiD, J. Chem. Phys., 1975, 63, 1605. [all data]

Emel'yanov, Peredvigina, et al., 1971
Emel'yanov, A.M.; Peredvigina, V.A.; Gorokhov, L.N., Ionization potentials of Li₂ and Na₂ molecules and the dissociation energy of Li₂⁺ and Na₂⁺ ions, Teplofiz. Vysokikh Temperatur, 1971, 9, 190, In original 164. [all data]

Foster, Leckenby, et al., 1969
Foster, P.J.; Leckenby, R.E.; Robbins, E.J., The ionization potentials of clustered alkali metal atoms, J. Phys. B:, 1969, 2, 478. [all data]

Velasco, 1960
Velasco, R., Espectro ultravioleta de la molecula Li₂, An. R. Soc. Esp. Fis. Quim., 1960, 175. [all data]

Barrow, Travis, et al., 1960
Barrow, R.F.; Travis, N.; Wright, C.V., Excited electronic states of lithium and sodium molecules, Nature, 1960, 187, 141. [all data]

Mercier, Rico, et al., 1969
Mercier, J.L.; Rico, F.R.; Velasco, R., Rotational analysis of some ultraviolet bands of the ⁷Li₂ molecule, Opt. Pura Apl., 1969, 2, 96. [all data]

Vance and Huffman, 1935
Vance, J.E.; Huffman, J.R., The ultraviolet absorption band of Li₂, Phys. Rev., 1935, 47, 215. [all data]

Sinha, 1948
Sinha, S.P., Ultra-violet bands of Li₂, Proc. Phys. Soc. London, 1948, 60, 443. [all data]

Rico, 1969
Rico, F.R., Aplicacion de los ordenadores electronicos al estudio de los espectros de absorcion de moleculas diatomicas. I. Calculo de las constantes vibracionales y rotacionales del sistema C¹π_µ - X¹Σ⁺_g de la molecula de litio, Opt. Pura Apl., 1969, 2, 1, 33-42. [all data]

Loomis and Nusbaum, 1931
Loomis, F.W.; Nusbaum, R.E., The magnetic rotation spectrum and heat of dissociation of the lithium molecule, Phys. Rev., 1931, 38, 1447. [all data]

McKellar, 1933
McKellar, A., Mass ratio of the lithium isotopes from the spectrum of Li₂, Phys. Rev., 1933, 44, 155. [all data]

Velasco, Ottinger, et al., 1969
Velasco, R.; Ottinger, Ch.; Zare, R.N., Dissociation energy of Li₂ from laser-excited fluorescence, J. Chem. Phys., 1969, 51, 5522. [all data]

Ottinger, Velasco, et al., 1970
Ottinger, Ch.; Velasco, R.; Zare, R.N., Some propensity rules in collision-induced rotational quantum jumps, J. Chem. Phys., 1970, 52, 1636. [all data]

Velasco, Ruano, et al., 1970
Velasco, R.; Ruano, O.; Rico, F.R., El sistema B-X de la molecula Li₂, Opt. Pura Apl., 1970, 3, 159. [all data]

Ottinger and Poppe, 1971
Ottinger, Ch.; Poppe, D., Collision-induced rotational and vibrational quantum jumps in electronically excited Li₂, Chem. Phys. Lett., 1971, 8, 513. [all data]

Almy and Irwin, 1936
Almy, G.M.; Irwin, G.R., Mass ratio of the lithium isotopes from the spectrum of Li₂, Phys. Rev., 1936, 49, 72. [all data]

Kutzelnigg, Staemmler, et al., 1972
Kutzelnigg, W.; Staemmler, V.; Gelus, M., Potential curve of the lowest triplet state of Li₂, Chem. Phys. Lett., 1972, 13, 496. [all data]

Logan, Cote, et al., 1952
Logan, R.A.; Cote, R.E.; Kusch, P., The sign of the quadrupole interaction energy in diatomic molecules, Phys. Rev., 1952, 86, 280. [all data]

Brooks, Anderson, et al., 1963
Brooks, R.A.; Anderson, C.H.; Ramsey, N.F., Rotational magnetic moments of diatomic alkalis, Phys. Rev. Lett., 1963, 10, 441. [all data]

King and Van Vleck, 1939
King, G.W.; Van Vleck, J.H., Dipole-dipole resonance forces, Phys. Rev., 1939, 55, 1165. [all data]

Olson and Konowalow, 1976
Olson, M.L.; Konowalow, D.D., The potential energy curve for the B¹Π_u state of Li₂, Chem. Phys. Lett., 1976, 39, 2, 281-284. [all data]

Kahn, Dunning, et al., 1977
Kahn, L.R.; Dunning, T.H., Jr.; Winter, N.W.; Goddard, W.A., III, The theoretical determination of the B¹Π_u potential energy curve for Li₂, J. Chem. Phys., 1977, 66, 1135. [all data]

Velasco, Ennen, et al., 1973
Velasco, R.; Ennen, G.; Ottinger, Ch., Λ splitting in vibrationally excited Li₂(B¹Π_u), Opt. Pura Apl., 1973, 6, 11. [all data]

Velasco and Morales, 1973
Velasco, R.; Morales, V., El sistema de bandas B-X en la molecula ⁶Li₂, Opt. Pura Apl., 1973, 6, 52. [all data]

Velasco and Rivero, 1972
Velasco, R.; Rivero, F., El sistema de bandas A-X en el espectro de la molecula ⁶Li₂, Opt. Pura Apl., 1972, 5, 76. [all data]

McKellar and Jenkins, 1939
McKellar, A.; Jenkins, F.A., The mass ratio of lithium isotopes from the red bands of Li₂, Publ. Dom. Astrophys. Obs. Victoria B.C., 1939, 7, 155. [all data]

Stwalley, 1976
Stwalley, W.C., The dissociation energy of ⁷Li₂, J. Chem. Phys., 1976, 65, 2038. [all data]

Lewis, 1931
Lewis, L.C., Die bestimmung des gleichgewichts zwischen den atomen und den molekulen eines alkalidampfes mit einer molekularstrahlmethode, Z. Phys., 1931, 69, 786. [all data]

Velasco, 1973
Velasco, R., Productos de disociacion de las series ¹Π de Li₂ Y Na₂, Opt. Pura Apl., 1973, 6, 16. [all data]

Krupenie, Mason, et al., 1963
Krupenie, P.H.; Mason, E.A.; Vanderslice, J.T., Interaction energies and transport coefficients of Li+H and O+H gas mixtures at high temperatures, J. Chem. Phys., 1963, 39, 2399. [all data]

Dixon, Gole, et al., 1977
Dixon, D.A.; Gole, J.L.; Jordan, K.D., Ab initio study of the electronic structure of Li₂^-, J. Chem. Phys., 1977, 66, 567. [all data]

Andersen and Simons, 1976
Andersen, E.; Simons, J., A calculation of the electron affinity of the lithium molecule, J. Chem. Phys., 1976, 64, 4548. [all data]

Notes

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Symbols used in this document:

IE (evaluated) Recommended ionization energy
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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