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Silicon dimer


Gas phase thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Quantity Value Units Method Reference Comment
Deltafgas589.94kJ/molReviewChase, 1998Data last reviewed in March, 1967
Quantity Value Units Method Reference Comment
gas,1 bar229.80J/mol*KReviewChase, 1998Data last reviewed in March, 1967

Gas Phase Heat Capacity (Shomate Equation)

Cp° = A + B*t + C*t2 + D*t3 + E/t2
H° − H°298.15= A*t + B*t2/2 + C*t3/3 + D*t4/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t2/2 + D*t3/3 − E/(2*t2) + G
    Cp = heat capacity (J/mol*K)
    H° = standard enthalpy (kJ/mol)
    S° = standard entropy (J/mol*K)
    t = temperature (K) / 1000.

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Temperature (K) 298. - 1100.1100. - 6000.
A 24.1998847.92605
B 31.58280-4.345921
C -8.2623131.037265
D -3.875582-0.072474
E 0.150614-0.208383
F 581.9149571.7143
G 250.9182280.7259
H 589.9440589.9440
ReferenceChase, 1998Chase, 1998
Comment Data last reviewed in March, 1967 Data last reviewed in March, 1967

Constants of diatomic molecules

Go To: Top, Gas phase thermochemistry data, References, Notes

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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

Data collected through August, 1977

Symbols used in the table of constants
SymbolMeaning
State electronic state and / or symmetry symbol
Te minimum electronic energy (cm-1)
ωe vibrational constant – first term (cm-1)
ωexe vibrational constant – second term (cm-1)
ωeye vibrational constant – third term (cm-1)
Be rotational constant in equilibrium position (cm-1)
αe rotational constant – first term (cm-1)
γe rotation-vibration interaction constant (cm-1)
De centrifugal distortion constant (cm-1)
βe rotational constant – first term, centrifugal force (cm-1)
re internuclear distance (Å)
Trans. observed transition(s) corresponding to electronic state
ν00 position of 0-0 band (units noted in table)
Diatomic constants for 28Si2
StateTeomegaeomegaexeomegaeyeBealphaegammaeDebetaereTrans.nu00
P 3Pig,i b 1          P larrow D R 53132.4 H
missing citation
b 1          P larrow D R 53173.5 H
missing citation
b 1    [(0.224)]     [(2.32)] P larrow D R 53219.2 H
missing citation
O 3Sigmau- 53395.58 404.2 H 3.0  0.2225 2 0.003  [0.050E-5]  2.327 O larrow X R 53341.94 Z
missing citation
StateTeomegaeomegaexeomegaeyeBealphaegammaeDebetaereTrans.nu00
N 3Sigmau- 46789.10 458.6 H 4.8  0.2193 0.0025  [0.023E-5]  2.344 N larrow X R 46762.21 Z
missing citation; missing citation
L 3Pig,i x+28629 3 [494] H   [0.2370]     [2.255] L lrarrow D 4 R 28602.2 5
missing citation; Dubois and Leclercq, 1971
K 3Sigmau- 30794.0 462.6 Z 5.95 H  0.2186 0.00316    2.348 K larrow X 6 R 30768.8 7
missing citation
H 3Sigmau- 24429.15 275.30 8 Z 1.99  0.1712 8 9 0.00135  0.030E-5  2.653 H lrarrow X 6 R 24311.32 8 Z
missing citation; missing citation; Dubois and Leclercq, 1971
StateTeomegaeomegaexeomegaeyeBealphaegammaeDebetaereTrans.nu00
D 3Piu,i x 10 547.94 Z 2.43  0.2596 0.00155    2.155 (D larrow X) 11 (34730) 11
Milligan and Jacox, 1970
X 3Sigmag- 0 510.98 Z 2.02  0.2390 0.00135  0.021E-5  2.246  

Notes

1Only v=0 observed.
2Spin splitting constants lambda0 = -6.68 (slight J dependence), gamma0 = +0.030.
3A = -22.6 (from A" and the observed subband origins).
4The 3Pi0 subbands are essentially complete, but only fragments of the other subbands have been observed.
5Average of the 3Pi0 and 3Pi2 subband origins. Douglas, 1955 gives 28059.1 which refers to the 0-1 rather than 0-0 band.
6Also observed in rare gas matrices Weltner and McLeod, 1964, Milligan and Jacox, 1970.
7Extrapolated from the origins of the 1-0 and 2-0 bands. The 0-0 band (vH = 30771) is completely diffuse.
8Corrected vibrational numbering of Dubois and Leclercq, 1971.
9The rotational lines of absorption bands having v'=6 are diffues, indication predissociation above 25877 cm-1. Higher levels have not been observed.
10A = -71.6 (from the effective B values).
11Progression of absorption bands in argon matrix, 34700 - 36300 cm-1; tentative interpretation Milligan and Jacox, 1970.
12From the observed predissociation in H Verma and Warsop, 1963 and thermochemical data [mass-spectrometry Drowart, DeMaria, et al., 1958, recalculated Verhaegen, Stafford, et al., 1964].
13A = -28.2.

References

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

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

Chase, 1998
Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

Dubois and Leclercq, 1971
Dubois, I.; Leclercq, H., Absorption spectrum of Si2 in the visible and near-ultraviolet region, Can. J. Phys., 1971, 49, 3053. [all data]

Milligan and Jacox, 1970
Milligan, D.E.; Jacox, M.E., Infrared and ultraviolet spectra of the products of the vacuum-ultraviolet photolysis of silane isolated in an argon matrix, J. Chem. Phys., 1970, 52, 2594. [all data]

Douglas, 1955
Douglas, A.E., The spectrum of the Si2 molecule, Can. J. Phys., 1955, 33, 801. [all data]

Weltner and McLeod, 1964
Weltner, W., Jr.; McLeod, D., Jr., Spectroscopy of Silicon Carbide and Silicon Vapors Trapped in Neon and Argon Matrices at 4° and 20°K, J. Chem. Phys., 1964, 41, 1, 235, https://doi.org/10.1063/1.1725627 . [all data]

Verma and Warsop, 1963
Verma, R.D.; Warsop, P.A., The absorption spectrum of the Si2 molecule, Can. J. Phys., 1963, 41, 152. [all data]

Drowart, DeMaria, et al., 1958
Drowart, J.; DeMaria, G.; Inghram, M.G., Thermodynamic study of SiC utilizing a mass spectrometer, J. Chem. Phys., 1958, 29, 1015. [all data]

Verhaegen, Stafford, et al., 1964
Verhaegen, G.; Stafford, F.E.; Drowart, J., Mass spectrometric study of the systems boron-carbon and boron-carbon-silicon, J. Chem. Phys., 1964, 40, 1622. [all data]


Notes

Go To: Top, Gas phase thermochemistry data, Constants of diatomic molecules, References