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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 August, 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 12C1H
RydbergSeveral unassigned absorption bands 1 above 80000 cm-1.
Herzberg and Johns, 1969
Rydberg series joining on to G, nu = 85850 -R/(n-0.09)2; n = 3,4,5,6
missing citation
G [74373] 2          G larrow X 72960
missing citation
F 2Sigma+ [65945]    [12.17] 3     [1.221] F larrow X R 64531.5 4 Z
missing citation
E 2Pi [65625]    [12.6] 5     [1.2] E larrow X R 64211.7 4 Z
missing citation
D 2Pii [60394] 6    [13.7] 5     [1.15] D larrow B V 33282.8 4 Z
missing citation
           D larrow X 58981 4 Z
missing citation
C 2Sigma+ 31801.5 2840.2 Z 125.96 7 13.55 14.603 8 9 0.7185 10  [0.001555] 11  1.1143 C lrarrow X 12 13 VR 31778.1 4 Z
Heimer, 1932; Gero, 1941; missing citation; Herzberg and Johns, 1969
B 2Sigma- (26044) [1794.9] 14 Z   [12.645] 15 9 16  [0.00222] 17  [1.1975] B lrarrow X 18 13 R 25698.2 4 Z
missing citation; Gero, 1941; missing citation; missing citation
A 2Delta 23189.8 19 2930.7 Z 96.65  14.934 20 9 0.697  0.00154 0.00004 1.1019 A lrarrow X 21 13 V 23217.5 4 Z
Gero, 1941; Kiess and Broida, 1956; missing citation; missing citation
a 4Sigma- (5844) (3145) (72)  (15.4) (0.55)    (1.085)  5985 22
Kasdan, Herbst, et al., 1975
X 2Pir 0 23 2858.5 Z 63.02  14.457 24 25 9 0.534  0.00145  1.1199 26  
Rydbeck, Ellder, et al., 1973
Ab initio calculations
Meyer and Rosmus, 1975


1According to theoretical work Walker and Kelly, 1972 they represent the nf series.
23d complex consisting of 2Sigma, 2Pi, 2Delta.
3Spin splitting constant gamma0= +0.62. Heterogeneous predissociation.
4The band origins refer to the zero points of the Hill-Van Vleck formulae for the ground and excited (Lambda neq 0) states. See also Garstang, 1963.
5Homogeneous predissociation.
6A= -28.5.
7omegaeze = -3.957; from CD using isotope relations.
8Spin splitting constant gamma ~ +0.05 Herzberg and Johns, 1969, Botterud, Lofthus, et al., 1973. Predissociation, see 12.
9Slightly different sets of constants from the same data are given by Botterud, Lofthus, et al., 1973 for X, A, B, C and Krupp, 1974 for X, A. Precise values for the rotational energy levels of X 2Pi(v=0) in Douglas and Elliott, 1965; tables of term values for levels of X, A, B,C in Botterud, Lofthus, et al., 1973.
10alphav= +0.0258(v+1/2)2 - 0.023(v+1/2)3; see 7 .
11D1 = 16.7E-4, D2 = 20E-4.
12Lifetime of C 2Sigma+ anomalously small on account of predissociation Hesser and Lutz, 1968, Herzberg and Johns, 1969, Hesser and Lutz, 1970, Elander and Smith, 1973. According to Brzozowski, Bunker, et al., 1976 the lifetime in v=0 varies from 10 ns at N=1 to 25 ns at N=24 and is even shorter in v=1. The previous observation of different lifetimes for F1 and F2 levels is not confirmed. The lifetime for CD is more than twice that for CH Hesser and Lutz, 1970 indicating that predissociation is weaker Herzberg and Johns, 1969. Ab initio theory Hinze, Lie, et al., 1975 gives a radiative lifetime tau(v=0) = 89 ns Hinze, Lie, et al., 1975 suggesting that the radiationless and the radiative transition probabilities are approximately in the ratio 8 to 1 Brzozowski, Bunker, et al., 1976. From absorption experiments Linevsky, 1967 an f value of f= 0.006 Linevsky, 1967 was derived for the C-X transition.
13Wavenumber and wavelength tables and comparisons with the solar spectrum published by Moore and Broida, 1959. 13CH lines for A-X measured by Richter and Tonner, 1967 and used to determine 13C/12C ratio in the sun. Franck-Condon factors Halmann and Laulicht, 1966, Liszt and Smith, 1972. The laboratory absorption spectrum was first observed by Norrish, Porter, et al., 1953 in the acetylene combustion initiated by the flash photolysis of NO2; in flames by Gaydon, Spokes, et al., 1960; and more recently by Bleekrode and Nieuwpoort, 1965, Bleekrode, 1966, Herzberg and Johns, 1969.
14Very shallow potential curve; omegae ~ 2251, omegaexe ~ 230 (from CD). A small potential maximum has been established in this state Herzberg and Johns, 1969; confirmed by theoretical calculations Lie, Hinze, et al., 1972.
15Spin splitting constant gamma0= -0.0285 Gero, 1941, gamma1 = -0.020 Herzberg and Johns, 1969. Breaking off in emission above v'=0, N'=15 and v'=1, N'=6 and broadening in absorption at higher N' due to predissociation; see also 18. Selective excitation of v'=1 in hydrogen flames and suppression of breaking off Durie, 1952.
16B1= 11.160.
17D1= 32.8E-4.
18Radiative lifetime tau= 0.38 mus Fink and Welge, 1967, Linevsky, 1967, Hesser and Lutz, 1970 corresponding to f~0.0029 Fink and Welge, 1967, Linevsky, 1967, Hesser and Lutz, 1970. Brooks and Smith, 1974 and Brzozowski, Bunker, et al., 1976 have measured lifetimes of individual rotational lines finding a regular increase from 0.32 to 0.38 mus from N'=2 to 14 (v'=0); sudden drop to 0.12 mus for N'=15 due to predissociation: see, however, Anderson, Peacher, et al., 1975. In v'= 1 the lifetime is 0.40 mus until breaking off occurs between N'= 6 and 7.
19A= -1.02 Herzberg and Johns, 1969, see also Kiess and Broida, 1956, Botterud, Lofthus, et al., 1973.
20Stark effect, muel(v=0) = 0.89 D Scarl and Dalby, 1974.
21Lifetime tau(v=0) = 0.534 mus Brzozowski, Bunker, et al., 1976 corresponding to f=0.0053 Brzozowski, Bunker, et al., 1976: superseding earlier less precise values by Bennett and Dalby, 1960, Fink and Welge, 1967, Hesser and Lutz, 1970, Smith, 1971, Jorgensen and Sorensen, 1975. Kuz'menko, Kuzyakov, et al., 1972 from shock tube absorption measurements obtain fe = 0.0019 Kuz'menko, Kuzyakov, et al., 1972. A theoretical f00 = 0.0068 Hinze, Lie, et al., 1975 is given in Hinze, Lie, et al., 1975. The observation of a reduced lifetime in v=1 for N>11 Brzozowski, Bunker, et al., 1976 suggests a weak predissociation probably caused by X 2Pi.
22T0, from laser photoelectron spectrometry of CH- Kasdan, Herbst, et al., 1975. Theoretical calculations Lie, Hinze, et al., 1972 give 5395 cm-1. The vibrational and rotational constants given are theoretical values; see also Liu and Verhaegen, 1970.
23A = +27.95. Slightly higher values in Goss, 1966 and Botterud, Lofthus, et al., 1973.
24Lambda-type doubling, Deltav ~ 0.038N(N+1) - .... For the lowest J values more complicated formulae apply, see Douglas and Elliott, 1965 and Goss, 1966. The transition between the two Lambda components of J=1/2 has been observed with its hyperfine structure in emission in interstellar clouds Rydbeck, Ellder, et al., 1973. The derived J=1/2 Lambda-doublet separation is 3320.987 MHz, close to earlier predictions by Douglas and Elliott, 1965, Baird and Bredohl, 1971 and a subsequent theoretical calculation by Hammersley and Richards, 1974. Predicted Lambda- doubling and hyperfine splittings for other J values in Levy and Hinze, 1975.
25Stark effect, muel = 1.46 D Phelps and Dalby, 1966.
26Lambda doubling sp. 24
27From the predissociation in the B state Herzberg and Johns, 1969 as modified by Brooks and Smith, 1974 and Brzozowski, Bunker, et al., 1976. Confirmed thermochemically by Brewer and Kester, 1964.
28From Rydberg series Herzberg and Johns, 1969. Theoretical photoionization cross section Walker and Kelly, 1972, 2.


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

Herzberg and Johns, 1969
Herzberg, G.; Johns, J.W.C., New spectra of the CH molecule, Astrophys. J., 1969, 158, 399. [all data]

Heimer, 1932
Heimer, T., Untersuchung uber die kohlenwasserstoffbande «lambda»3143, Z. Phys., 1932, 78, 771. [all data]

Gero, 1941
Gero, L., Vervollstandigung der analyse der CH-Banden, Z. Phys., 1941, 118, 27. [all data]

Kiess and Broida, 1956
Kiess, N.H.; Broida, H.P., Analysis of the (0, 1) and (1, 2) bands of the 2«DELTA»-2«PI» system of CH, Astrophys. J., 1956, 123, 166. [all data]

Kasdan, Herbst, et al., 1975
Kasdan, A.; Herbst, E.; Lineberger, W.C., Laser photoelectron spectrometry of CH2-, Chem. Phys. Lett., 1975, 31, 78. [all data]

Rydbeck, Ellder, et al., 1973
Rydbeck, O.E.H.; Ellder, J.; Irvine, W.M., Radio detection of interstellar CH, Nature (London), 1973, 246, 466. [all data]

Meyer and Rosmus, 1975
Meyer, W.; Rosmus, P., PNO-Cl and CEPA studies of electron correlation effects. III. Spectroscopic constants and dipole moment functions for the ground states of the first-row and second-row diatomic hydrides, J. Chem. Phys., 1975, 63, 2356. [all data]

Walker and Kelly, 1972
Walker, T.E.H.; Kelly, H.P., Rydberg states of CH, J. Chem. Phys., 1972, 57, 936. [all data]

Garstang, 1963
Garstang, R.H., Revised molecular constants for the CH and CD spectra, Proc. Phys. Soc. London, 1963, 82, 545. [all data]

Botterud, Lofthus, et al., 1973
Botterud, I.; Lofthus, A.; Veseth, L., Term values and molecular parameters for CH and CH+, Phys. Scr., 1973, 8, 218. [all data]

Krupp, 1974
Krupp, B.M., A new analysis of the A2«DELTA»-X2«PI» system of CH, Astrophys. J., 1974, 189, 389. [all data]

Douglas and Elliott, 1965
Douglas, A.E.; Elliott, G.A., Laboratory investigations of the interstellar radio-frequency lines of CH and other molecules, Can. J. Phys., 1965, 43, 496. [all data]

Hesser and Lutz, 1968
Hesser, J.E.; Lutz, B.L., Direct measurements of predissociation probabilities in CH and CD molecules, Phys. Rev. Lett., 1968, 20, 363. [all data]

Hesser and Lutz, 1970
Hesser, J.E.; Lutz, B.L., Probabilities for radiation and predissociation. II. The excited states of CH, CD, and CH+, and some astrophysical implications, Astrophys. J., 1970, 159, 703. [all data]

Elander and Smith, 1973
Elander, N.; Smith, W.H., Predissociation in the C2«SIGMA»+ state of CH and its astrophysical implications, Astrophys. J., 1973, 184, 663-670. [all data]

Brzozowski, Bunker, et al., 1976
Brzozowski, J.; Bunker, P.; Elander, N.; Erman, P., Predissocation effects in the A, B, and C states of CH and the interstellar formation rate of CH via inverse predissociation, Astrophys. J., 1976, 207, 414. [all data]

Hinze, Lie, et al., 1975
Hinze, J.; Lie, G.C.; Liu, B., Valence excited states of CH. III. Radiative lifetimes, Astrophys. J., 1975, 196, 621. [all data]

Linevsky, 1967
Linevsky, M.J., Relative oscillator strengths of CH. The heat of dissocaition of CH, J. Chem. Phys., 1967, 47, 3485. [all data]

Moore and Broida, 1959
Moore, C.E.; Broida, H.P., CH in the solar spectrum, J. Res. Nat. Bur. Stand. Sect. A, 1959, 63, 19. [all data]

Richter and Tonner, 1967
Richter, J.; Tonner, K.-F., Bestimmung des Haufigkeitsverhaltnisses C12/C13 in der Sonnenatmosphare, Z. Astrophys., 1967, 67, 155. [all data]

Halmann and Laulicht, 1966
Halmann, M.; Laulicht, I., Isotope effects on vibrational transition probabilities. IV. Electronic transitions of isotopic C2, CO, CN, H2, and CH molecules, Astrophys. J. Suppl. Ser., 1966, 12, 307. [all data]

Liszt and Smith, 1972
Liszt, H.S.; Smith, W.H., RKR Franck-Condon factors for blue and ultraviolet transitions of some molecules of astrophysical interest and some comments on the interstellar abundance of CH, CH+, and SiH, J. Quant. Spectrosc. Radiat. Transfer, 1972, 12, 947. [all data]

Norrish, Porter, et al., 1953
Norrish, R.G.W.; Porter, G.; Thrush, B.A., Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy. I. Free radical absorption spectra in acetylene combustion, Proc. R. Soc. London A, 1953, 216, 165. [all data]

Gaydon, Spokes, et al., 1960
Gaydon, A.G.; Spokes, G.N.; Suchtelen, J.V., Absorption spectra of low-pressure flames, Proc. R. Soc. London A, 1960, 256, 323. [all data]

Bleekrode and Nieuwpoort, 1965
Bleekrode, R.; Nieuwpoort, W.C., Absorption and emission measurements of C2 and CH electronic bands in low-pressure oxyacetylene flames, J. Chem. Phys., 1965, 43, 3680. [all data]

Bleekrode, 1966
Bleekrode, Thesis, Amsterdam, 1966, 0. [all data]

Lie, Hinze, et al., 1972
Lie, G.C.; Hinze, J.; Liu, B., Calculated a 4«SIGMA»-, A2«DELTA», B2«SIGMA»- states of CH, J. Chem. Phys., 1972, 57, 625. [all data]

Durie, 1952
Durie, R.A., The excitation and intensity distribution of CH bands in flames, Proc. Phys. Soc. London Sect. A, 1952, 65, 125. [all data]

Fink and Welge, 1967
Fink, E.H.; Welge, K.H., Lifetime measurements on CH(A2«DELTA»), CH(B2«SIGMA»-), and C2(A3«PI»g) by the phase-shift method, J. Chem. Phys., 1967, 46, 4315. [all data]

Brooks and Smith, 1974
Brooks, N.H.; Smith, W.H., Radiative and predissociation probabilities for individual rotational levels of the B2«SIGMA»- state of CH with application to the radiative recombination of CH in the interstellar medium, Astrophys. J., 1974, 194, 513. [all data]

Anderson, Peacher, et al., 1975
Anderson, R.A.; Peacher, J.; Wilcox, D.M., Radiative lifetime of the B2«SIGMA»- state of CH, J. Chem. Phys., 1975, 63, 5287. [all data]

Scarl and Dalby, 1974
Scarl, E.A.; Dalby, F.W., High field Stark effects in CH and NH, Can. J. Phys., 1974, 52, 1429. [all data]

Bennett and Dalby, 1960
Bennett, R.G.; Dalby, F.W., Experimental oscillator strength of CH and NH, J. Chem. Phys., 1960, 32, 1716. [all data]

Smith, 1971
Smith, W.H., Absolute oscillator strengths for the CH+, CD+, and BH A1«PI»-X1«SIGMA»+ transition, J. Chem. Phys., 1971, 54, 1384. [all data]

Jorgensen and Sorensen, 1975
Jorgensen, S.W.; Sorensen, G., Radiative lifetimes in molecules studied by means of fast, molecular ion beams, J. Chem. Phys., 1975, 62, 2550. [all data]

Kuz'menko, Kuzyakov, et al., 1972
Kuz'menko, N.E.; Kuzyakov, Yu.Ya.; Kuznetsova, L.A.; Kudryumova, I.N.; Chuev, B.N., Experimental determination of the oscillator strength in the A2«DELTA»-X2«PI» electron transition for the carbon monohydride (CH) molecule, High Temp. Engl. Transl., 1972, 9, 823, In original 905. [all data]

Liu and Verhaegen, 1970
Liu, H.P.D.; Verhaegen, G., Electronic states of CH and NH+, J. Chem. Phys., 1970, 53, 735. [all data]

Goss, 1966
Goss, W.M., A new determination of the frequency of the interstellar radio line of CH, Astrophys. J., 1966, 145, 3, 707-714. [all data]

Baird and Bredohl, 1971
Baird, K.M.; Bredohl, H., A laboratory determination of the frequency of the 10-centimeter radio line of CH by optical measurements, Astrophys. J., 1971, 169, 83. [all data]

Hammersley and Richards, 1974
Hammersley, R.E.; Richards, W.G., «LAMBDA»-type doubling in the CH molecule, Nature (London), 1974, 251, 597-598. [all data]

Levy and Hinze, 1975
Levy, D.H.; Hinze, J., Hyperfine and «LAMBDA»-doubling splitting in excited rotational levels of CH, Astrophys. J., 1975, 200, 236. [all data]

Phelps and Dalby, 1966
Phelps, D.H.; Dalby, F.W., Experimental determination of the electric dipole moment of the ground electronic state of CH, Phys. Rev. Lett., 1966, 16, 3. [all data]

Brewer and Kester, 1964
Brewer, R.G.; Kester, F.L., Dissociation energy of the CH radical, J. Chem. Phys., 1964, 40, 812. [all data]

Walker and Kelly, 1972, 2
Walker, T.E.H.; Kelly, H.P., The photoionization cross section for diatomic CH, Chem. Phys. Lett., 1972, 16, 511. [all data]


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