Silicon dimer
- Formula: Si2
- Molecular weight: 56.1710
- IUPAC Standard InChI: InChI=1S/Si2/c1-2
- IUPAC Standard InChIKey: NTQGILPNLZZOJH-UHFFFAOYSA-N
- CAS Registry Number: 12597-35-2
- Chemical structure:
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Gas phase thermochemistry data
Go To: Top, Gas phase ion energetics data, Constants of diatomic molecules, References, Notes
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 |
|---|---|---|---|---|---|
| ΔfH°gas | 141.00 | kcal/mol | Review | Chase, 1998 | Data last reviewed in March, 1967 |
| Quantity | Value | Units | Method | Reference | Comment |
| S°gas,1 bar | 54.924 | cal/mol*K | Review | Chase, 1998 | Data 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 (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.
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| Temperature (K) | 298. to 1100. | 1100. to 6000. |
|---|---|---|
| A | 5.783911 | 11.45460 |
| B | 7.548471 | -1.038701 |
| C | -1.974740 | 0.247912 |
| D | -0.926286 | -0.017322 |
| E | 0.035998 | -0.049805 |
| F | 139.0810 | 136.6430 |
| G | 59.97089 | 67.09510 |
| H | 141.0000 | 141.0000 |
| Reference | Chase, 1998 | Chase, 1998 |
| Comment | Data last reviewed in March, 1967 | Data last reviewed in March, 1967 |
Gas phase ion energetics data
Go To: Top, Gas phase thermochemistry data, Constants of diatomic molecules, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
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
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess
View reactions leading to Si2+ (ion structure unspecified)
Electron affinity determinations
| EA (eV) | Method | Reference | Comment |
|---|---|---|---|
| 2.230 ± 0.010 | N/A | Peppernick, Gunaratne, et al., 2010 | Stated electron affinity is the Vertical Detachment Energy; B |
| 2.202 ± 0.010 | LPES | Arnold, Kitsopoulos, et al., 1993 | B |
| 2.199 ± 0.012 | LPES | Nimlos, Harding, et al., 1987 | B |
| <2.60011 | IMRB | Mandich, Bondybey, et al., 1987 | The values from this reference are ca. 0.4-0.8 eV more bound than from other references; B |
Ionization energy determinations
| IE (eV) | Method | Reference | Comment |
|---|---|---|---|
| 7.9 | LS | Winstead, Paukstis, et al., 1995 | LL |
| ≤8.04 ± 0.13 | DER | Boo and Armentrout, 1987 | LBLHLM |
| 7.3 | EI | Verhaegen, Stafford, et al., 1964 | RDSH |
| 7.4 ± 0.3 | EI | Drowart, DeMaria, et al., 1958 | RDSH |
Constants of diatomic molecules
Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics 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
| Symbol | Meaning |
|---|---|
| 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) |
| State | Te | ωe | ωexe | ωeye | Be | αe | γe | De | βe | re | Trans. | ν00 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| P 3Πg,i | b 1 | P ← D R | 53132.4 H | |||||||||
| ↳missing citation | ||||||||||||
| b 1 | P ← D R | 53173.5 H | ||||||||||
| ↳missing citation | ||||||||||||
| b 1 | [(0.224)] | [(2.32)] | P ← D R | 53219.2 H | ||||||||
| ↳missing citation | ||||||||||||
| O 3Σu- | 53395.58 | 404.2 H | 3.0 | 0.2225 2 | 0.003 | [0.050E-5] | 2.327 | O ← X R | 53341.94 Z | |||
| ↳missing citation | ||||||||||||
| State | Te | ωe | ωexe | ωeye | Be | αe | γe | De | βe | re | Trans. | ν00 |
| N 3Σu- | 46789.10 | 458.6 H | 4.8 | 0.2193 | 0.0025 | [0.023E-5] | 2.344 | N ← X R | 46762.21 Z | |||
| ↳missing citation; missing citation | ||||||||||||
| L 3Πg,i | x+28629 3 | [494] H | [0.2370] | [2.255] | L ↔ D 4 R | 28602.2 5 | ||||||
| ↳missing citation; Dubois and Leclercq, 1971 | ||||||||||||
| K 3Σu- | 30794.0 | 462.6 Z | 5.95 H | 0.2186 | 0.00316 | 2.348 | K ← X 6 R | 30768.8 7 | ||||
| ↳missing citation | ||||||||||||
| H 3Σu- | 24429.15 | 275.30 8 Z | 1.99 | 0.1712 8 9 | 0.00135 | 0.030E-5 | 2.653 | H ↔ X 6 R | 24311.32 8 Z | |||
| ↳missing citation; missing citation; Dubois and Leclercq, 1971 | ||||||||||||
| State | Te | ωe | ωexe | ωeye | Be | αe | γe | De | βe | re | Trans. | ν00 |
| D 3Πu,i | x 10 | 547.94 Z | 2.43 | 0.2596 | 0.00155 | 2.155 | (D ← X) 11 | (34730) 11 | ||||
| ↳Milligan and Jacox, 1970 | ||||||||||||
| X 3Σg- | 0 | 510.98 Z | 2.02 | 0.2390 | 0.00135 | 0.021E-5 | 2.246 | |||||
Notes
| 1 | Only v=0 observed. |
| 2 | Spin splitting constants λ0 = -6.68 (slight J dependence), γ0 = +0.030. |
| 3 | A = -22.6 (from A" and the observed subband origins). |
| 4 | The 3Π0 subbands are essentially complete, but only fragments of the other subbands have been observed. |
| 5 | Average of the 3Π0 and 3Π2 subband origins. Douglas, 1955 gives 28059.1 which refers to the 0-1 rather than 0-0 band. |
| 6 | Also observed in rare gas matrices Weltner and McLeod, 1964, Milligan and Jacox, 1970. |
| 7 | Extrapolated from the origins of the 1-0 and 2-0 bands. The 0-0 band (vH = 30771) is completely diffuse. |
| 8 | Corrected vibrational numbering of Dubois and Leclercq, 1971. |
| 9 | The rotational lines of absorption bands having v'=6 are diffues, indication predissociation above 25877 cm-1. Higher levels have not been observed. |
| 10 | A = -71.6 (from the effective B values). |
| 11 | Progression of absorption bands in argon matrix, 34700 - 36300 cm-1; tentative interpretation Milligan and Jacox, 1970. |
| 12 | From 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]. |
| 13 | A = -28.2. |
References
Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics 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]
Peppernick, Gunaratne, et al., 2010
Peppernick, S.J.; Gunaratne, K.D.D.; Sayres, S.G.; Castleman, A.W.,
Photoelectron imaging of small silicon cluster anions, Si-n- (n=2-7),
J. Chem. Phys., 2010, 132, 4, 044302, https://doi.org/10.1063/1.3299271
. [all data]
Arnold, Kitsopoulos, et al., 1993
Arnold, C.C.; Kitsopoulos, T.N.; Neumark, D.M.,
Reassignment of the Si2(-) Photodetachment Spectra,
J. Chem. Phys., 1993, 99, 1, 766, https://doi.org/10.1063/1.465757
. [all data]
Nimlos, Harding, et al., 1987
Nimlos, M.R.; Harding, L.B.; Ellison, G.B.,
The Electronic States of Si2 and Si2- as Revealed by Photoelectron Spectroscopy,
J. Chem. Phys., 1987, 87, 9, 5116, https://doi.org/10.1063/1.453679
. [all data]
Mandich, Bondybey, et al., 1987
Mandich, M.L.; Bondybey, V.E.; Reents, W.D.,
Reactive Etching of Positive and Negative Silicon Cluster Ions by Nitrogen Dioxide,
J. Chem. Phys., 1987, 86, 7, 4245, https://doi.org/10.1063/1.451885
. [all data]
Winstead, Paukstis, et al., 1995
Winstead, C.B.; Paukstis, S.J.; Walters, J.L.; Gole, J.L.,
Multiphoton ionization of Ag2: Assessment of a new excited electronic state and resolution of the Ag2 ionization potential,
J. Chem. Phys., 1995, 102, 1877. [all data]
Boo and Armentrout, 1987
Boo, B.H.; Armentrout, P.B.,
Reaction of silicon ion (2P) with silane (SiH4, SiD4) heats of formation of SiHn, SiHn+ (n=1,2,3), and Si2Hn+ (n=0,1,2,3) remarkable isotope exchange reaction involving four hydrogen shifts,
J. Am. Chem. Soc., 1987, 109, 3549. [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]
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]
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]
Notes
Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Constants of diatomic molecules, References
- Symbols used in this document:
EA Electron affinity S°gas,1 bar Entropy of gas at standard conditions (1 bar) ΔfH°gas Enthalpy of formation of gas at standard conditions - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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