Selenium dimer

Formula: Se₂
Molecular weight: 157.92
IUPAC Standard InChI: InChI=1S/Se2/c1-2
IUPAC Standard InChIKey: XIMIGUBYDJDCKI-UHFFFAOYSA-N
CAS Registry Number: 12185-17-0
Chemical structure:
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Gas phase ion energetics data

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

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
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess

View reactions leading to Se₂⁺ (ion structure unspecified)

Electron affinity determinations

EA (eV)	Method	Reference	Comment
1.940 ± 0.070	LPES	Snodgrass, Coe, et al., 1989	B

Ionization energy determinations

IE (eV)	Method	Reference	Comment
8.6	PE	Potts and Novak, 1983	LBLHLM
8.9 ± 0.2	EI	Grade, Wienecke, et al., 1983	LBLHLM
8.70 ± 0.05	PE	Streets and Berkowitz, 1976	LLK
~8.84	S	Barrow, Burton, et al., 1970	RDSH
8.88 ± 0.03	PI	Berkowitz and Chupka, 1969	RDSH
8.93	PE	Potts and Novak, 1983	Vertical value; LBLHLM

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
Se⁺	12.0 ± 0.5	Se	EI	Uy and Drowart, 1969	RDSH
Se⁺	13. ± 13.	Se	PI	Berkowitz and Chupka, 1969	RDSH
Se⁺	12.6 ± 0.5	Se	EI	Uy, Muenow, et al., 1968	RDSH

Constants of diatomic molecules

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

Data collected through July, 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 ⁸⁰Se₂
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
F (1_u)	(55421)	[430.2] H									(F ← X₂) V	54932.8 H
F (1_u)	↳Barrow, Burton, et al., 1970
E 0_u⁺	54752.5	403.9 H	1.3		0.0924	0.00033				2.13₇	E ← X₂ 1 V	54249
	↳Barrow, Burton, et al., 1970; Greenwood and Barrow, 1976
											E ← X₁ V	54761.7 H
	↳Barrow, Burton, et al., 1970
D (1_u)	(53075)	[426.2] H			[0.0965]					[2.09₁]	D ← X₁ 2 V	53096.1 H
D (1_u)	↳missing citation
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
C₂ ³Σ^-_0+u	(53324)	[414] H	3								C₂ ← X₁ V	53339 H
C₂ ³Σ^-_0+u	↳Barrow, Burton, et al., 1970
C₁ ³Σ^-_1u	53220.5	428.0 H	1.22		0.09664	0.00033₃				2.089₄	C₁ ← X₂ V	52730.9 Z
C₁ ³Σ^-_1u	↳missing citation
B₂ ³Σ^-_1u	26058.₆	246.42 4 Z	1.225		0.07086 5 6	0.00055₃		(2E-8)		2.440₀	B₂ ↔ X₂ 7 8 R	25478.₂ 9
	↳Barrow, Chandler, et al., 1966
											B₂ → X₁ R	25989.₂
	↳Gouedard and Lehmann, 1976; Greenwood and Barrow, 1976
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
B₁ ³Σ^-_0u+	25980.36	246.291 4 10 Z	1.016	-0.00549	0.07048 11	0.000345		(4E-8)		2.446₆	B₁ → X₂ R	25399.8
	↳Gouedard and Lehmann, 1976; Greenwood and Barrow, 1976
											B₁ ↔ X₁ 8 R	25910.84 Z
	↳missing citation
X₂ ³Σ^-_1g	510.0 12	387.156 13 Z	0.9640 13		0.09019 13 14	0.000299 13		(2E-8)		2.162₈	15
X₁ ³Σ^-_0g+	0	385.303 Z	0.9636₃	-0.000881₄	0.08992	0.000288	-6.1E-7	2.4E-8	-0.023E-8	2.166₀

Notes

This transition is much weaker than E←X₁.

The assumption Barrow, Burton, et al., 1970 that this transition is C₁←X₁ has been withdrawn Greenwood and Barrow, 1976 since it gives the wrong X₁-X₂ splitting.

Diffuse bands

Vibrational analysis confirmed by isotope investigations Barrow, Chandler, et al., 1966.

Average value, B_e(F₃) - B_e(F₂) = +0.00038.

Rotational perturbations; a tentative analysis Yee and Barrow, 1972 of these and similar perturbations in the 0_u⁺ component was based on an erroneous value of the 0_u⁺ - 1_u splitting. Predissociation in v=5 at J=72(F₃) and 73(F₂); bands with v'=6 have not been seen.

Lifetime τ(v=0,J=105) = 58 ns, from Hanle effect measurements Dalby, Vigue, et al., 1975, Gouedard and Lehmann, 1975 combined with experimentally determined Lande g_J factors Gouedard and Lehmann, 1975, Gouedard and Lehmann, 1977.

Various proposed other "systems" in the region 14500 -18500 cm^-1 Rosen and Monfort, 1936, Leelavathi and Rao, 1955 have been shown Barrow, Chandler, et al., 1966 to belong to the main B-X system. Yee and Barrow, 1972 have extended the rotational analysis of the ⁷⁸Se₂ bands to higher values of v".

Extrapo1ated from bands having v"≥8, using lower state constants of Barrow, Beattie, et al., 1971.

The B₁ 0_u⁺ state has a substantial potential maximum arising from an avoided crossing with a repulsive 0_u⁺ state. The interaction strongly affects vibrational levels above v=15; the theoretical discussion by Atabek and Lefebvre, 1972 predicts irregular level shifts and widths above the crossing point.

Sharp predissociation limits occur for v=4(J=106), v=5(J=82), v=6(J=50), leading to a dissociation limit at 27508 cm^-1 above X₁ 0_g⁺(v=0), and for v=13(J=96), v=14(J=78), v=15(J=50), leading to a dissociation limit at 29498 cm^-1. Barrow, Chandler, et al., 1966 attribute the former to ³P₂ + ³P₁, the latter to ³P₁ + ³P₁. There are many rotational perturbations and several accidental predissociations; see also 6.

From Greenwood and Barrow, 1976 whose measurements of fluorescence series in the range 6≤ v"≤12 lead to Δv = +509.95 + 2.125₆(v+1/2) for the separation of the rotationless 1_g and 0_g⁺ substates.

Constants apply to 8≤v≤29.

Average of F₂ and F₃, B_e(F₃) - B_e(F₂) = +0.00006.

For a theoretical calculation of the magnetic moment of Se₂, consistent with experimental results, see Buchler and Meschi, 1975.

From the predissociation in B₁ 0_u⁺ (see 11) three possible spectroscopic values for the dissociation energy of ⁸⁰Se₂, i.e. D₀⁰ = 3.410₅, 3.163₈, 3.096₄ eV, can be derived depending on the assumed atomic states at the observed predissociation limits. Barrow, Chandler, et al., 1966 prefer D₀⁰ = 3.164 eV on the basis of indirect spectroscopic arguments. However, both photoionization Berkowitz and Chupka, 1969, Radler and Berkowitz, 1977 and thermochemical studies [mass-spectrometry Berkowitz and Chupka, 1966, Colin and Drowart, 1968, Uy and Drowart, 1969, Knudsen-torsion effusion Budininkas, Edwards, et al., 1968; see also Meschi and Searcy, 1969, Smoes, Mandy, et al., 1972] strongly favor the higher value D₀⁰ = 3.411 eV.

Photoionization mass-spectrometry Berkowitz and Chupka, 1969. From the photoelectron spectrum Streets and Berkowitz, 1976 derive adiabatic and vertical ionization potentials of 8.70 and 8.89 eV, respectively.

References

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Snodgrass, Coe, et al., 1989
Snodgrass, J.T.; Coe, J.V.; McHugh, K.M.; Freidhoff, C.B.; Bowen, K.H., Photoelectron Spectroscopy of the Selenium and Tellurium Containing Negative Ions: SeO₂^-, Se₂^- and Te₂^-, J. Phys. Chem., 1989, 93, 4, 1249, https://doi.org/10.1021/j100341a016 . [all data]

Potts and Novak, 1983
Potts, A.W.; Novak, I., Ultraviolet photoelectron spectra of selenium and tellurium, J. Electron Spectrosc. Relat. Phenom., 1983, 28, 267. [all data]

Grade, Wienecke, et al., 1983
Grade, M.; Wienecke, J.; Rosinger, W.; Hirschwald, W., Electron impact investigation of the molecules SeS(g) and TeSe(g) under high-temperature equilibrium conditions, Ber. Bunsen-Ges. Phys. Chem., 1983, 87, 355. [all data]

Streets and Berkowitz, 1976
Streets, D.G.; Berkowitz, J., Photoelectron spectroscopy of Se₂ and Te₂, J. Electron Spectrosc. Relat. Phenom., 1976, 9, 269. [all data]

Barrow, Burton, et al., 1970
Barrow, R.F.; Burton, W.G.; Callomon, J.H., Absorption spectrum of gaseous 80Se₂ in the region 51500-55000 cm-1, J. Chem. Soc. Faraday Trans., 1970, 66, 2685. [all data]

Berkowitz and Chupka, 1969
Berkowitz, J.; Chupka, W.A., Photoionization of high-temperature vapors. VI. S₂, Se₂, and Te₂, J. Chem. Phys., 1969, 50, 4245. [all data]

Uy and Drowart, 1969
Uy, O.M.; Drowart, J., Mass spectrometric determination of the dissociation energies of the molecules BiO, BiS, BiSe and BiTe, J. Chem. Soc. Faraday Trans., 1969, 65, 3221. [all data]

Uy, Muenow, et al., 1968
Uy, O.M.; Muenow, D.W.; Ficalora, P.J.; Margrave, J.L., Mass spectrometric studies at high temperatures. Part 30. Vaporization of Ga₂S₃, Ga₂Se₃ and Ga₂Te₃, and stabilities of the gaseous gallium chalcogenides, J. Chem. Soc. Faraday Trans., 1968, 64, 2998. [all data]

Greenwood and Barrow, 1976
Greenwood, D.J.; Barrow, R.F., A medium-resolution study of fluorescence in ⁸⁰Se₂ excited by lines of the argon-ion laser, J. Phys. B:, 1976, 9, 2123. [all data]

Barrow, Chandler, et al., 1966
Barrow, R.F.; Chandler, G.G.; Meyer, C.B., The B(³Σ_u^-) - X(³Σ_g^-) band system of the Se₂ molecule, Philos. Trans. R. Soc. London A, 1966, 260, 395. [all data]

Gouedard and Lehmann, 1976
Gouedard, G.; Lehmann, J.C., Fine-structure determinations in the X³Σ_g^- and B³Σ_u^- states of ⁸⁰Se₂, J. Phys. B:, 1976, 9, 2113. [all data]

Yee and Barrow, 1972
Yee, K.K.; Barrow, R.F., Absorption and fluorescence spectra of gaseous Se₂, J. Chem. Soc. Faraday Trans. 2, 1972, 68, 1181. [all data]

Dalby, Vigue, et al., 1975
Dalby, F.W.; Vigue, J.; Lehmann, J.C., On Hanle effects in the B(³Σ_u^-)-X(³Σ_g^-) band system of the Se₂ molecule, Can. J. Phys., 1975, 53, 140. [all data]

Gouedard and Lehmann, 1975
Gouedard, G.; Lehmann, J.-C., Effet hanle et resonances en lumiere modulee sur le niveau B1_u,v'=O, J'=105 de la molecule (⁸⁰Se)₂ excitee par la raie 4 727 Å d'un laser a argon ionise, C.R. Acad. Sci. Paris, Ser. B, 1975, 280, 471. [all data]

Gouedard and Lehmann, 1977
Gouedard, G.; Lehmann, J.C., Lande factors measurements in the B³Σ_u^- state of ⁸⁰Se₂, J. Phys. Lett., 1977, 38, 85. [all data]

Rosen and Monfort, 1936
Rosen, B.; Monfort, F., Etude du spectre du selenium dans le rouge et l'infrarouge photographique, Physica (The Hague), 1936, 3, 257. [all data]

Leelavathi and Rao, 1955
Leelavathi, V.; Rao, P.T., The visible emission spectrum of Se₂, Indian J. Phys., 1955, 29, 1. [all data]

Barrow, Beattie, et al., 1971
Barrow, R.F.; Beattie, I.R.; Burton, W.G.; Gilson, T., Resonance fluorescence spectra of ⁸⁰Se₂, Trans. Faraday Soc., 1971, 67, 583. [all data]

Atabek and Lefebvre, 1972
Atabek, O.; Lefebvre, R., Evaluation of the level shifts produced on the discrete levels of the BO_u⁺ state of the Se₂ molecule by the interaction with a repulsive state, Chem. Phys. Lett., 1972, 17, 167. [all data]

Buchler and Meschi, 1975
Buchler, A.; Meschi, D.J., The magnetic moment of Se₂, J. Chem. Phys., 1975, 63, 3586. [all data]

Radler and Berkowitz, 1977
Radler, K.; Berkowitz, J., Photoionization mass spectrometric study of CSe₂, J. Chem. Phys., 1977, 66, 2176. [all data]

Berkowitz and Chupka, 1966
Berkowitz, J.; Chupka, W.A., Equilibrium composition of selenium vapor; the thermodynamics of the vaporization of HgSe, CdSe, and SrSe, J. Chem. Phys., 1966, 45, 4289. [all data]

Colin and Drowart, 1968
Colin, R.; Drowart, J., Mass spectrometric determination of dissociation energies of gaseous indium sulphides, selenides and tellurides, J. Chem. Soc. Faraday Trans., 1968, 64, 2611. [all data]

Budininkas, Edwards, et al., 1968
Budininkas, P.; Edwards, R.K.; Wahlbeck, P.G., Dissociation energies of group VIa gaseous homonuclear diatomic molecules. II. Selenium, J. Chem. Phys., 1968, 48, 2867. [all data]

Meschi and Searcy, 1969
Meschi, D.J.; Searcy, A.W., Investigation of the magnetic moments of S₂, Se₂, Te₂, Se₆, and Se₅ by the Stern-Gerlach magnetic deflection method, J. Chem. Phys., 1969, 51, 5134. [all data]

Smoes, Mandy, et al., 1972
Smoes, S.; Mandy, F.; Vander Auwera-Mahieu, A.; Drowart, J., Determination by the mass spectrometric Knudsen cell method of the dissociation energies of the group IB chalcogenides, Bull. Soc. Chim. Belg., 1972, 81, 45. [all data]

Notes

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Symbols used in this document:

AE Appearance energy

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