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 July, 1977

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 (85)Rb2
Unidentified features in the absorption spectrum of rubidium vapour at 37270 and 40590 cm-1.
Creek and Marr, 1968
Diffuse absorption bands corresponding to van der Waals molecules.
Ny-Tsi-Ze and Shang-Yi, 1938
D 22777.5 40.42 H 0.0745 -0.00144       D ← X 1 R 22769.1 H
Tsi-Ze and San-Tsiang, 1937
C 1Πu 20835.1 36.46 H 0.124 2        C ↔ X 1 3 R 20824.7 H
Tsi-Ze and San-Tsiang, 1937
"Quasicontinuous" emission 16400 - 18500 cm-1.
Brom and Broida, 1974
B 1Πu 14662.6 48.05 H 0.191        B ↔ X 4 R 14657.9 H
Kusch, 1936
A (1Σu+) 5           A ↔ X 
Sorokin and Lankard, 1971; Kostin and Khodovoi, 1973; Drummond and Schlie, 1976
X 1Σg+ 0 57.31 H 0.105         
Mol. beam magn. reson. 6


1Lifetime measurements by Baumgartner, Demtroder, et al., 1970 vary from 61 ns to l4 ns, the former attributed to the D state, the latter to C 1Πu. The two states have also been observed in two-photon ionization of Rb2 Granneman, Klewer, et al., 1976.
2Predissociation 9
3Polarization studies of the fluorescence spectrum Feldman and Zare, 1976, Tam and Happer, 1976 confirm its composition of P and R as well as Q lines, contrary to the conclusions of Brom and Broida, 1974 that it consists of Q line progressions only.
4Magnetic rotation spectrum Kusch, 1936. The B → X (and A → X) emission observed by Brom and Broida, 1974 is attributed to atomic recombination of Rb(52P) and Rb(52S), the former formed in the predissociation of Rb2 C 1Πu.
5Unresolved band system 9200 - 12500 cm-1. 10
6gJ(85Rb2) = 0.00953 μN Brooks, Anderson, et al., 1963; eqQ(85Rb) = -1.10 MHz Logan, Cote, et al., 1952.
7Spectroscopic value Tsi-Ze and San-Tsiang, 1937, extrapolation of vibrational levels in X,C,D.
8Associative photoionization of rubidium vapour by atomic line absorption Lawrence and Edlefsen, 1929, Lee and Mahan, 1965, Hudson, 1965.
9The state responsible for the partial predissociation (≤ ~25%) of C 1Πu correlates with the 5p 2P3/2 state of Rb Brom and Broida, 1974, Feldman and Zare, 1976; see also Collins, Curry, et al., 1976 whose observations of the diffuse and sharp series of Rb in two-photon ionization of rubidium vapor through intermediate continuum states of Rb2 include only transitions from the 2P3/2 component.
10Interference by the a 3Πu state may be responsible for irregularities in the spectrum at 9900 cm-1 Drummond and Schlie, 1976.
11Rough estimate based on the analysis of charge exchange cross sections Olson, 1969. Theoretical calculations predict re = 4.45 Å Bellomonte, Cavaliere, et al., 1974.


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

Creek and Marr, 1968
Creek, D.M.; Marr, G.V., Some ultraviolet cross-section measurements on molecular alkali-metal vapours, J. Quant. Spectrosc. Radiat. Transfer, 1968, 8, 1431. [all data]

Ny-Tsi-Ze and Shang-Yi, 1938
Ny-Tsi-Ze, P.; Shang-Yi, C., Bandes d'absorption du rubidium et du cesium en presence des gaz etrangers, J. Phys. Radium, 1938, 9, 5, 169-171. [all data]

Tsi-Ze and San-Tsiang, 1937
Tsi-Ze, N.; San-Tsiang, T., Band spectra and energy of dissociation of the rubidium molecule, Phys. Rev., 1937, 52, 91. [all data]

Brom and Broida, 1974
Brom, J.M., Jr.; Broida, H.P., Laser photoluminescence and photopredissociation of Rb2, J. Chem. Phys., 1974, 61, 982. [all data]

Kusch, 1936
Kusch, P., The band spectra of rubidium and of its combinations with other alkali metals, Phys. Rev., 1936, 49, 218. [all data]

Sorokin and Lankard, 1971
Sorokin, P.P.; Lankard, J.R., Emission spectra of alkali-metal molecules observed with a heat-pipe discharge tube, J. Chem. Phys., 1971, 55, 3810. [all data]

Kostin and Khodovoi, 1973
Kostin, N.N.; Khodovoi, V.A., Excitation kinetics of molecular vapor of alkali metals by intense optical radiation, Bull. Acad. Sci. USSR, Phys. Ser. Engl. Transl., 1973, 37, 69, In original 2093. [all data]

Drummond and Schlie, 1976
Drummond, D.L.; Schlie, L.A., Spectra and kinetics of the Rb2 molecule, J. Chem. Phys., 1976, 65, 2116. [all data]

Baumgartner, Demtroder, et al., 1970
Baumgartner, G.; Demtroder, W.; Stock, M., Lifetime-measurements of alkali-molecules excited by different laserlines, Z. Phys., 1970, 232, 462. [all data]

Granneman, Klewer, et al., 1976
Granneman, E.H.A.; Klewer, M.; Nygaard, K.J.; van der Wiel, M.J., Two-photon ionization of Cs2, Rb2 and RbCs using an Ar-ion laser, J. Phys. B:, 1976, 9, 865. [all data]

Feldman and Zare, 1976
Feldman, D.L.; Zare, R.N., Evidence for predissociation of Rb2*(C1Πu) into Rb*(2P3/2) and Rb(2S1/2), Chem. Phys., 1976, 15, 415. [all data]

Tam and Happer, 1976
Tam, A.C.; Happer, W., Polarization of laser-excited fluorescent lines from 85Rb2 and 87Rb2 molecules, J. Chem. Phys., 1976, 64, 4337. [all data]

Brooks, Anderson, et al., 1963
Brooks, R.A.; Anderson, C.H.; Ramsey, N.F., Rotational magnetic moments of diatomic alkalis, Phys. Rev. Lett., 1963, 10, 441. [all data]

Logan, Cote, et al., 1952
Logan, R.A.; Cote, R.E.; Kusch, P., The sign of the quadrupole interaction energy in diatomic molecules, Phys. Rev., 1952, 86, 280. [all data]

Lawrence and Edlefsen, 1929
Lawrence, E.O.; Edlefsen, N.E., The photo-ionization of the vapors of caesium and rubidium, Phys. Rev., 1929, 34, 233. [all data]

Lee and Mahan, 1965
Lee, Y.-T.; Mahan, B.H., Photosensitized ionization of alkali-metal vapors, J. Chem. Phys., 1965, 42, 2893. [all data]

Hudson, 1965
Hudson, R.D., Measurements of the molecular absorption cross section and the photoionization of sodium vapor between 1600 and 3700, J. Chem. Phys., 1965, 43, 1790. [all data]

Collins, Curry, et al., 1976
Collins, C.B.; Curry, S.M.; Johnson, B.W.; Mirza, M.Y.; Chellehmalzadeh, M.A.; Anderson, J.A.; Popescu, D.; Popescu, I., Multiphoton ionization of rubidium, Phys. Rev. A: Gen. Phys., 1976, 14, 1662. [all data]

Olson, 1969
Olson, R.E., Determination of the difference potential from resonant charge-exchange total cross sections: analysis of Rb+-Rb and Cs+-Cs, Phys. Rev., 1969, 187, 153. [all data]

Bellomonte, Cavaliere, et al., 1974
Bellomonte, L.; Cavaliere, P.; Ferrante, G., Alkali molecular ion energies and expectation values in a model-potential treatment, J. Chem. Phys., 1974, 61, 3225. [all data]


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