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Constants of diatomic molecules

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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 September, 1976

Symbols used in the table of constants
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 35Cl2
Rydberg series joining on to P: v(1-0) = 93200 - R / (n-0.54)2, n = 3...7; fragmentary vibrational structure.
Iczkowski, Margrave, et al., 1960
Fragments of additional band systems in absorption at v > 65000 cm-1.
Lee and Walsh, 1959; Iczkowski, Margrave, et al., 1960
Emission continua in the ultraviolet with maxima at 32640, 33810, 34700, 35450, 36220, 36820, 38970, 41140, 42500, 43710, 45500, 46610, 47670; 50060, 51850, 53890 cm-1. 1
Asundi and Venkateswarlu, 1947
P (74405) (621) (3)        P ← X 74436
Lee and Walsh, 1959; Iczkowski, Margrave, et al., 1960
O     [0.1840] 2      O → X R 74018.5 2 Z
missing citation
N     [0.1193] 2      N → X R 73363.3 2 Z
missing citation
M (72853) (636) (4)        M ← X 72891
Lee and Walsh, 1959
K (64024) (460)         K → X 3 63975
Haranath and Rao, 1958
J (61638) (520) (3)        J ← X 61618
Lee and Walsh, 1959
I 61438 262.3 H 0.812        I → B V 43632 H
Khanna, 1959
H (59432) (510)         H ← X 59408
Lee and Walsh, 1959
G (58629) (208)         G → X 3 R 58454
Haranath and Rao, 1958
F (58263) (442)         F ← X 58205
Lee and Walsh, 1959
E 57953 249.75 H 0.875        E ↔ B R 40140.0 H
Venkateswarlu and Khanna, 1959; missing citation; Wieland, Tellinghuisen, et al., 1972
D (53568) (440) (1.5)        D ← X 53508
Lee and Walsh, 1959
Cordes and Sponer, 1930; Lee and Walsh, 1959
C 1Πu 5          C ↔ X 6 
Gibson and Bayliss, 1933; Sulzer and Wieland, 1952; Jacobs and Giedt, 1965; Clyne and Stedman, 1968; Palmer and Carabetta, 1968
B 3Π0+u 17809 259.5 7 H 5.3 8  0.16256 9 0.00212 -0.000091 2.365E-7 10  2.4354 B ↔ X 11 12 R 17658 7 H
missing citation; missing citation; missing citation
A (3Π1u) (17440) (265) H (5)        A → X 11 13 
Coxon, 1973
A' (3Π2u) (17160) 14 (280) 15         A' → X 16 
Bondybey and Fletcher, 1976
X 1Σg+ 0 559.72 17 18 2.675 -0.0067 0.24399 17 0.00149 -0.0000017 1.86E-7  1.9879 19  
Winkel, Hunt, et al., 1969
Raman sp.
Holzer, Murphy, et al., 1970; Hochenbleicher and Schrotter, 1971; Hendra and Vear, 1972; Wallart, 1972; Edwards, Good, et al., 1976


1They have been interpreted Asundi and Venkateswarlu, 1947 as being due to transitions from stable excited states at 58000 (possibly F), 67700 and 75000 cm-1 to the repulsive states arising from 2P + 2P. The upper states at 67700 and 75000 cm-1 are considered to be 1g states and, therefore, are not observed in absorption from the ground state.
2Upper levels of four extensive resonance series Rao and Venkateswarlu, 1962, Douglas and Hoy, 1975. The v' values are uncertain. The resonance fluorescence spectrum is excited by the Cl I lines at 73983 and 73344 cm-1 in a discharge through Cl2 and involves transitions to ground state levels with v"≤59. The ground state dissociation energy derived from these resonance series Douglas and Hoy, 1975 agrees now very well with the more accurate value from the B-X system.
3These systems [called J-X and H-X by Haranath and Rao, 1958] have not been observed in absorption. For this reason Lee and Walsh, 1959 suggest that they may actually be due to Cl2+.
4Continuous absorption above ~52600 cm-1 at high pressure.
5Continuous absorption with maximum at 30500 cm-1.
6The angular distribution of photo-fragments confirms the assignment of the upper state of the continuum to 1Πu Busch, Mahoney, et al., 1969; see also Child and Bernstein, 1973 and Brith, Rowe, et al., 1975. The B ← X transition, however, contributes to the weak low-frequency region of the continuum; for a discussion of quantitative data see Coxon, 1973.
7Since high resolution data Douglas, Moller, et al., 1963, Clyne and Coxon, 1970 are available only for v≥5, the constants given here are from the low resolution emission work of Clyne and Coxon, 1967 (band heads); they are valid only for 0≤v≤6. For 6<v<22, Richards and Barrow, 1962 give ωe = 259.57, ωexe = 4.753, ωeye = -0.0677, ωeze = +0.00212. The band origin of the 6-0 band is at 18993.79 cm-1.
8Convergence limit 20879.64 ± 0.14 cm-1 Le Roy, 1973, LeRoy, 1974. See LeRoy and Bernstein, 1971, Goscinski, 1972, LeRoy, 1972, Yee and Stone, 1973, LeRoy, 1974 and the review in Le Roy, 1973 for relation of high vibrational levels to long-range internuclear potential.
9These constants are based on bands with 5≤v'≤13 Clyne and Coxon, 1970. Bv values up to v=31 have been determined Douglas, Moller, et al., 1963, Clyne and Coxon, 1970.
10+0.225E-7(v+1/2) + 0.015E-7(v+1/2)2 See 9 .
11Estimated radiative lifetimes in Coxon, 1973.
12Franck-Condon factors from RKR potentia1s Coxon, 1971. For a discussion of the repulsive part of the potential see Child and Bernstein, 1973.
13Two weak progressions, not belonging to B-X and tentatively assigned as 1-v" and 2-v" with v" = 8,9,..., were observed in the chlorine atom recombination spectrum and in the spectrum of the nitrogen trichloride decomposition flame; see references in Coxon, 1973.
14Not observed in the gas phase (see 16); in an Ar matrix this new state is located 650 cm-1 below the B 3Π0+u state.
15Estimated from isotope shifts.
16Long-lived (~76 ms in Ar) emission in rare gas matrices from v=0 of a new low-lying state following excitation into the B or C state; see Bondybey and Fletcher, 1976.
17These constants are based on the lowest six vibrational levels Clyne and Coxon, 1970. The following Dunham coefficients have been derived by Douglas and Hoy, 1975 from a detailed analysis at high resolution of the resonance series excited by the Cl I lines at 1351.7 and 1363.5 ; they represent all levels up to v=40: Y10 = 559.7507 Y01 = 0.244153 Y20 = -2.694271 Y11 = -0.0015163 Y30 = -3.32527E-3 Y21 = -3.9078E-6 Y40 = -2.27337E-4 Y31 = 7.0811E-8 Y50 = -3.92041E-6 Y41 = -5.5875E-9 Y60 = -6.02984E-8 Y02 = -1.9195E-7 Y00 = -0.0351 Y32 = -3.1678E-12 The same authors give, in addition, G(v) and Bv values up to v=59 and have determined an accurate RKR potential function. The long-range portion agrees very well with that predicted from theory.
18550.8 in liquid Cl2 Wallart, 1972; 554.6 in solid argon Ault, Howard, et al., 1975, Bondybey and Fletcher, 1976.
19Pressure induced IR absorption at 549 cm-1
20From the convergence limit in B 3Π0+ (see 8). From the same limit Le Roy, 1973 gives D00 = 19997.l4 cm-1 or 2.479349 eV presumably by using a different value for the 2P1/2 - 2P3/2 energy difference in Cl I. Here we used 882.36 cm-1 from Radziemski and Kaufman, 1969.
21From the photoelectron spectrum; average of Cornford, Frost, et al., 1971 and Potts and Price, 1971. Photoionization Watanabe, Nakayama, et al., 1962, in agreement with the Rydberg series, yields 11.48 eV.


Go To: Top, 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.

Iczkowski, Margrave, et al., 1960
Iczkowski, R.P.; Margrave, J.L.; Green, J.W., Absorption spectrum of chlorine in the vacuum ultraviolet, J. Chem. Phys., 1960, 33, 1261. [all data]

Lee and Walsh, 1959
Lee, J.; Walsh, A.D., The vacuum ultra-violet absorption spectra of the halogen molecules, Trans. Faraday Soc., 1959, 55, 1281. [all data]

Asundi and Venkateswarlu, 1947
Asundi, R.K.; Venkateswarlu, P., Spectra of the Halogens, I2, Br2 and Cl2, Indian J. Phys., 1947, 21, 101-118. [all data]

Haranath and Rao, 1958
Haranath, P.B.V.; Rao, P.T., Band spectra of iodine, chlorine, and bromine in the spectral region 2400-1400 A, J. Mol. Spectrosc., 1958, 2, 428. [all data]

Khanna, 1959
Khanna, B.N., Emission spectrum of chlorine excited in the presence of argon, Proc. Indian Acad. Sci. Sect. A, 1959, 49, 293-301. [all data]

Venkateswarlu and Khanna, 1959
Venkateswarlu, P.; Khanna, B.N., Emission spectrum of chlorine excited in the presence of argon. Part I. The band system in the region 2600-2390 Å, Proc. Indian Acad. Sci. Sect. A, 1959, 49, 117-127. [all data]

Wieland, Tellinghuisen, et al., 1972
Wieland, K.; Tellinghuisen, J.B.; Nobs, A., The band systems E → B(4000-4360 Å) and F → X(2530-2740 Å) of 127I2 and 129I2, and the corresponding system E = B of Br2 and Cl2, J. Mol. Spectrosc., 1972, 41, 69. [all data]

Cordes and Sponer, 1930
Cordes, H.; Sponer, H., Die molekulabsorption des chlors, broms, jodchlorids und jodbromids im aubersten ultraviolett, Z. Phys., 1930, 63, 334. [all data]

Gibson and Bayliss, 1933
Gibson, G.E.; Bayliss, N.S., Variation with temperature of the continuous absorption spectrum of diatomic molecules: Part I. Experimental, the absorption spectrum of chlorine, Phys. Rev., 1933, 44, 188. [all data]

Sulzer and Wieland, 1952
Sulzer, P.; Wieland, K., Intensitatsverteilung eines kontinuierlichen Absorptions-spectrums in Abhangigkeit von Temperatur und Wellenzahl, Helv. Phys. Acta, 1952, 25, 653-676. [all data]

Jacobs and Giedt, 1965
Jacobs, T.A.; Giedt, R.R., Absorption coefficients of Cl2 at high temperatures, J. Quant. Spectrosc. Radiat. Transfer, 1965, 5, 457. [all data]

Clyne and Stedman, 1968
Clyne, M.A.A.; Stedman, D.H., Recombination of ground-state halogen atoms. Part 1. Radiative recombination of chlorine atoms, Trans. Faraday Soc., 1968, 64, 1816. [all data]

Palmer and Carabetta, 1968
Palmer, H.B.; Carabetta, R.A., Radiative recombination of chlorine atoms in shock waves: a re-examination, J. Chem. Phys., 1968, 49, 2466. [all data]

Coxon, 1973
Coxon, J.A., Chapt. 4. Low-lying electronic states of diatomic halogen molecules in Molecular Spectroscopy. Volume 1, Barrow,R.F.; Long,D.A.; Millen,D.J., ed(s)., The Chemical Society, Burlington House, London, W1V 0BN, 1973, 177-228. [all data]

Bondybey and Fletcher, 1976
Bondybey, V.E.; Fletcher, C., Photophysics of low lying electronic states of Cl2 in rare gas solids, J. Chem. Phys., 1976, 64, 3615. [all data]

Winkel, Hunt, et al., 1969
Winkel, R.G.; Hunt, J.L.; Clouter, M.J., Pressure-induced fundamental infrared absorption band of gaseous chlorine, J. Chem. Phys., 1969, 50, 1298. [all data]

Holzer, Murphy, et al., 1970
Holzer, W.; Murphy, W.F.; Bernstein, H.J., Resonance Raman effect and resonance fluoroscence in halogen gases, J. Chem. Phys., 1970, 52, 399. [all data]

Hochenbleicher and Schrotter, 1971
Hochenbleicher, G.; Schrotter, H.W., Observation of hot bands in the Raman spectra of Cl2 gas and CCl4 vapor, Appl. Spectrosc., 1971, 25, 3, 360-362. [all data]

Hendra and Vear, 1972
Hendra, P.J.; Vear, C.J., The pure rotational laser Raman spectrum of chlorine, Spectrochim. Acta, Part A, 1972, 28, 1949-1961. [all data]

Wallart, 1972
Wallart, F., Study of vibrational hot bands by Raman spectroscopy - application to chlorine and bromine chloride, Can. J. Spectrosc., 1972, 17, 128. [all data]

Edwards, Good, et al., 1976
Edwards, H.G.M.; Good, E.A.M.; Long, D.A., Pure rotational Raman spectra of the chlorine species, 35Cl2 and 35Cl37Cl, J. Chem. Soc. Faraday Trans. 2, 1976, 72, 927-933. [all data]

Rao and Venkateswarlu, 1962
Rao, Y.V.; Venkateswarlu, P., Vacuum ultraviolet resonance spectrum of Cl2 molecule, J. Mol. Spectrosc., 1962, 9, 173. [all data]

Douglas and Hoy, 1975
Douglas, A.E.; Hoy, A.R., The resonance fluorescence spectrum of Cl2 in the vacuum ultraviolet, Can. J. Phys., 1975, 53, 1965-1975. [all data]

Busch, Mahoney, et al., 1969
Busch, G.E.; Mahoney, R.T.; Morse, R.I., Translational spectroscopy: Cl2 photodissociation, J. Chem. Phys., 1969, 51, 449. [all data]

Child and Bernstein, 1973
Child, M.S.; Bernstein, R.B., Diatomic interhalogens: systematics and implications of spectroscopic interatomic potentials and curve crossings, J. Chem. Phys., 1973, 59, 5916. [all data]

Brith, Rowe, et al., 1975
Brith, M.; Rowe, M.D.; Schnepp, O.; Stephens, P.J., The magnetic circular dichroism spectrum of the halogen molecules I2, Br2, Cl2. Resolution of overlapping continua, Chem. Phys., 1975, 9, 57. [all data]

Douglas, Moller, et al., 1963
Douglas, A.E.; Moller, C.K.; Stoicheff, B.P., Can. J. Phys., 1963, 41, 1174. [all data]

Clyne and Coxon, 1970
Clyne, M.A.A.; Coxon, J.A., The visible band absorption spectrum of chlorine, J. Mol. Spectrosc., 1970, 33, 381. [all data]

Clyne and Coxon, 1967
Clyne, M.A.A.; Coxon, J.A., The formation and detection of some low-lying excited electronic states of BrCl and other halogens, Proc. R. Soc. London A, 1967, 298, 424. [all data]

Richards and Barrow, 1962
Richards, W.G.; Barrow, R.F., Rotational analysis of the A3Π0+,u - X1Σg+ system of the chlorine molecule, Proc. Chem. Soc. London, 1962, 297. [all data]

Le Roy, 1973
Le Roy, R.J., Chapt. 3. Energy levels of a diatomic near dissociation in Molecular Spectroscopy. Volume 1, Barrow,R.F.; Long,D.A.; Millen,D.J., ed(s)., The Chemical Society, Burlington House, London, W1V 0BN, 1973, 113-175. [all data]

LeRoy, 1974
LeRoy, R.J., Long-range potential coefficients from RKR turning points: C6 and C8 for B(3Π0u+)-state Cl2, Br2, and I2, Can. J. Phys., 1974, 52, 246. [all data]

LeRoy and Bernstein, 1971
LeRoy, R.J.; Bernstein, R.B., Dissociation energies and long-range potentials of diatomic molecules from vibrational spacings: the halogens, J. Mol. Spectrosc., 1971, 37, 109. [all data]

Goscinski, 1972
Goscinski, O., Outer vibrational turning points near dissociation in the B(3Π0u+) state of Br2 and Cl2, Mol. Phys., 1972, 24, 655. [all data]

LeRoy, 1972
LeRoy, R.J., Dependence of the diatomic rotational constant Bv on the long-range internuclear potential, Can. J. Phys., 1972, 50, 953. [all data]

Yee and Stone, 1973
Yee, K.K.; Stone, T.J., Analysis of RKR long-range potentials of the B3Π0u+ states of Br2 and Cl2, Mol. Phys., 1973, 26, 1169. [all data]

Coxon, 1971
Coxon, J.A., Franck-Condon factors and r-centroids for halogen molecules. I. The B3Π(0u+)-X1Σg+ system of 35Cl2, J. Quant. Spectrosc. Radiat. Transfer, 1971, 11, 1355. [all data]

Ault, Howard, et al., 1975
Ault, B.S.; Howard, W.F.; Andrews, L., Laser-induced fluorescence and Raman spectra of chlorine and bromine molecules isolated in inert matrices, J. Mol. Spectrosc., 1975, 55, 217. [all data]

Radziemski and Kaufman, 1969
Radziemski, L.J., Jr.; Kaufman, V., Wavelengths, energy levels, and analysis of neutral atomic chlorine (Cl I), J. Opt. Soc. Am., 1969, 59, 4, 424-443. [all data]

Cornford, Frost, et al., 1971
Cornford, A.B.; Frost, D.C.; McDowell, C.A.; Ragle, J.L.; Stenhouse, I.A., Photoelectron spectra of the halogens, J. Chem. Phys., 1971, 54, 2651. [all data]

Potts and Price, 1971
Potts, A.W.; Price, W.C., Photoelectron spectra of the halogens and mixed halides ICI and lBr, J. Chem. Soc. Faraday Trans., 1971, 67, 1242. [all data]

Watanabe, Nakayama, et al., 1962
Watanabe, K.; Nakayama, T.; Mottl, J., Ionization potentials of some molecules, J. Quant. Spectry. Radiative Transfer, 1962, 2, 369. [all data]


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