Diargon

Diargon
Names
	Other names argon dimer
Identifiers
CAS Number	12595-59-4 ;
3D model (JSmol)	Interactive image;
PubChem CID	6432035;
	InChI InChI=1S/2Ar Key: XMPZLAQHPIBDSO-UHFFFAOYSA-N;
	SMILES [Ar].[Ar];
Properties
Chemical formula	Ar2
Molar mass	79.896 g·mol−1
Appearance	transparent gas
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Diargon or the argon dimer is a molecule containing two argon atoms. Normally this is only very weakly bound together by van der Walls forces. However in an excited state, or ionised state, the two atoms can be tightly bound together, with significant spectral features.

Properties

The ionisation energy is 14.4558 eV (or 116593 cm⁻¹).^[1]

The dissociation energy of neutral Ar₂ in the ground state is 98.7 cm⁻¹^[2] which is hundreds of times weaker than that of typical molecules.^[3] Dissociation energy of Ar₂⁺ is 1.3144 eV or 10601 cm⁻¹.^[4]

Excited states

Neutral

99.6% of the argon isotopes are ⁴⁰Ar, so the spectrom observed in natural argon dimer will be due to the ⁴⁰Ar⁴⁰Ar isotopomer.^[5]

Parameter	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	ν₀₀	R_e Å	ref
H											112033.9
G											110930.9
F 0⁺ _g											108492.2
E											107330
D											106029.5
C 0⁺ _g											95050.7
B¹Σ_u⁺ 0⁺ _g											93241.26
A³Σ_2u⁺1_u											92393.3
X¹Σ_g⁺		31.92	3.31	0.11	0.060	0.004		76.9				3.8	^[5]^[3]

Cation

Parameter	breakup	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	ν₀₀	R_e Å	ref
D²Σ_1/2u⁺	Ar¹S₀ + Ar⁺²P_1/2
C²Π_1/2u	Ar¹S₀ + Ar⁺²P_1/2
B²Π_1/2g	Ar¹S₀ + Ar⁺²P_3/2
C²Π_3/2u	Ar¹S₀ + Ar⁺²P_3/2
B²Π_3/2g⁺	Ar¹S₀ + Ar⁺²P_3/2								0.104 eV					^[2]
A²Σ_1/2u⁺	Ar¹S₀ + Ar⁺²P_3/2		307.0	2.05					1.361 eV					^[4]^[2]

References

^ Dehmer, P. M.; Pratt, S. T. (15 January 1982). "Photoionization of argon clusters". The Journal of Chemical Physics. 76 (2): 843–853. doi:10.1063/1.443056.
^ ^a ^b ^c Pradeep, T.; Niu, B.; Shirley, D. A. (April 1993). "Photoelectron spectroscopy of rare gas dimers revisited: Vibrationally resolved photoelectron spectrum of argon dimer" (PDF). The Journal of Chemical Physics. 98 (7): 5269–5275. doi:10.1063/1.464926.
^ ^a ^b Ewing, George E. (June 1975). "Structure and Properties of van der Waals Molecules". Accounds of Chemical Research. 8 (6): 185–192.
^ ^a ^b Signorell, R.; Wüest, A.; Merkt, F. (22 December 1997). "The first adiabatic ionization potential of Ar2". The Journal of Chemical Physics. 107 (24): 10819–10822. doi:10.1063/1.474199.
^ ^a ^b Docken, Kate K.; Schafer, Trudy P. (June 1973). "Spectroscopic information on ground-state Ar2, Kr2, and Xe2 from interatomic potentials". Journal of Molecular Spectroscopy. 46 (3): 454–459. doi:10.1016/0022-2852(73)90057-X.

[1] Dehmer, P. M.; Pratt, S. T. (15 January 1982). "Photoionization of argon clusters". The Journal of Chemical Physics. 76 (2): 843–853. doi:10.1063/1.443056.

[prad-2] Pradeep, T.; Niu, B.; Shirley, D. A. (April 1993). "Photoelectron spectroscopy of rare gas dimers revisited: Vibrationally resolved photoelectron spectrum of argon dimer" (PDF). The Journal of Chemical Physics. 98 (7): 5269–5275. doi:10.1063/1.464926.

[ewing-3] Ewing, George E. (June 1975). "Structure and Properties of van der Waals Molecules". Accounds of Chemical Research. 8 (6): 185–192.

[sig-4] Signorell, R.; Wüest, A.; Merkt, F. (22 December 1997). "The first adiabatic ionization potential of Ar2". The Journal of Chemical Physics. 107 (24): 10819–10822. doi:10.1063/1.474199.

[kate-5] Docken, Kate K.; Schafer, Trudy P. (June 1973). "Spectroscopic information on ground-state Ar2, Kr2, and Xe2 from interatomic potentials". Journal of Molecular Spectroscopy. 46 (3): 454–459. doi:10.1016/0022-2852(73)90057-X.

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