Iron dimer

Formula: Fe₂
Molecular weight: 111.690
CAS Registry Number: 12596-01-9
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Gas phase ion energetics data

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Data compiled as indicated in comments:
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess

View reactions leading to Fe₂⁺ (ion structure unspecified)

Electron affinity determinations

EA (eV)	Method	Reference	Comment
0.9020 ± 0.0080	LPES	Leopold and Lineberger, 1986	B

Ionization energy determinations

IE (eV)	Method	Reference	Comment
6.30 ± 0.01	PI	Rohlfing, Cox, et al., 1984	LBLHLM
5.9 ± 0.2	EI	Lin and Kant, 1969	RDSH

Constants of diatomic molecules

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

Data collected through March, 1976

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 ⁽⁵⁶⁾Fe₂
State	T_e	ω_e	Trans.	ν₀₀
C 2			C ← X 1
C 2	↳de Vore, Ewing, et al., 1975
B		(218) 3	B ← X 1	(21095) 4
B	↳de Vore, Ewing, et al., 1975
A		(194) 3	A ← X 1	(18355) 4
A	↳de Vore, Ewing, et al., 1975
X	0

Notes

In Ar matrices at 10 K.

Continuous absorption with maximum at 24120 cm^-1.

Long upper state progression.

Lowest observed level, vibrational numbering unknown.

Thermochemical value (mass-spectrom.) Lin and Kant, 1969.

References

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Leopold and Lineberger, 1986
Leopold, D.G.; Lineberger, W.C., A study of the low-lying electronic states of Fe₂ and Co₂ by negative ion photoelectron spectroscopy, J. Chem. Phys., 1986, 85, 51. [all data]

Rohlfing, Cox, et al., 1984
Rohlfing, E.A.; Cox, D.M.; Kaldor, A.; Johnson, K.H., Photoionization spectra and electronic structure of small iron clusters, J. Chem. Phys., 1984, 81, 3846. [all data]

Lin and Kant, 1969
Lin, S.-S.; Kant, A., Dissociation energy of Fe, J. Phys. Chem., 1969, 73, 2450. [all data]

de Vore, Ewing, et al., 1975
de Vore, T.C.; Ewing, A.; Franzen, H.F.; Calder, V., The visible absorption spectra of Mn₂, Fe₂, and Ni₂ in argon matrices, Chem. Phys. Lett., 1975, 35, 78. [all data]

Notes

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Symbols used in this document:

EA Electron affinity
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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