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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 March, 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 14NH
Theoretical potential functions and spectroscopic constants for the ground and excited states: Cade and Huo, 1967 Das, Wahl, et al., 1974 Meyer and Rosmus, 1975; Kouba and Ohrn, 1970 O'Neil and Schaefer, 1971 Hay and Dunning, 1976.
d 1Σ+ 83160 2672.6 Z 71.2  14.390 1 0.621  16.0E-4 2  1.1163 d → c 3 4 V 39512.26 Z
missing citation; Narasimham and Krishnamurty, 1967; Whittaker, 1967; Krishnamurty and Narasimham, 1969; missing citation
c 1Π (43744) [2122.64] Z 5  14.537 6 7 8 0.593 9 -0.347 9 [22.0E-4] 10  1.1106 d → b 3 $mR 61619.60 Z
Whittaker, 1969; missing citation
           c → b 11 4 R 22106.62 Z
missing citation; missing citation
           c → a 11 4 R 30755.54 Z
Dieke and Blue, 1934; missing citation; Florent and Leach, 1952; missing citation
A 3Πi 29807.4 12 3231.2 Z 98.6  16.6745 13 14 8 0.7454  [17.80E-4] 15  1.03698 A ↔ X 16 4 17 29776.76 Z
Funke, 1935; missing citation; Murai and Shimauchi, 1966; Malicet, Brion, et al., 1970
b 1Σ+ 21202 3352.4 Z 74.24 18 0.70 16.705 19 0.591  16.0E-4 20  1.0360 b → X 21 17 21238 Z
Gilles, Masanet, et al., 1974
a 1Δ (12566) 22 [3188] Z (68) 23  [16.439] 8 0.66  [16.2E-4]  1.0341 (a-X) 12589 24
X 3Σ- 0 3282.27 Z 78.35  16.6993 25 0.6490  [17.097E-4] 26  1.03621 27  
Radford and Litvak, 1975; Wayne and Radford, 1976
Fundamental b. In matrices missing citation Rosengren and Pimentel, 1965


1 Krishnamurty and Narasimham, 1969 report a breaking-off in the d→c 1-1 band above J'=15 which they attribute to predissociation in the upper state. Intensity anomalies are confirmed Graham and Lew, 1978 for the d →c 1-1 and 1-0 bands, but higher rotational levels (except J'=l6) do emit in transitions to the b state Graham and Lew, 1978. Similar intensity perturbations are seen in other d→b and d→c bands.
2He = +10E-8.
3Radiative lifetime τ(v=0) = 18 ns Smith, 1969.
4Franck-Condon factors Smith and Liszt, 1971, Rao and Lakshman, 1973.
5ΔG(3/2) = 1694.08. The theoretical calculations of Kouba and Ohrn, 1970 predict a potential maximum resulting from the avoided crossing of the two 1Π states arising from N(2D)+H(2S) and N(2P)+H(2S).
6Λ-type doubling Δ vef(v=0) = +0.0165J(J+l).
7Predissociation by rotation in v=0 above J=22 and in v=1 above J=15 Krishnamurty and Narasimham, 1969, Graham and Lew, 1978. A much weaker predissociation, not seen on the photographic plates but detected by high-resolution lifetime measurements [ Smith, Brzozowski, et al., 1976, see 11], affects the lower J levels of both v=0 and 1 and may be caused by interaction with the unstable 5Σ- state arising from ground state atomic products. All rotational structure in v=2 is diffuse except for J=1.
8Electric dipole moments of a 1Δ, A 3Π, c 1Π = 1.49, 1.31, 1.70 D, respectively Irwin and Dalby, 1965; see also Huo, 1968.
9 Graham and Lew, 1978.
10D1 = 26.6E-4 Graham and Lew, 1978, D2 = 51.0E-4 Graham and Lew, 1978; H0 = -26E-8 Graham and Lew, 1978, H1= -115E-8 Graham and Lew, 1978.
11Lifetime τ(v=0,J=2) = 411 ns Smith, Brzozowski, et al., 1976, decreasing with increasing rotation to 226 ns for J=l7 owing to weak predissociation; in v=1 the longest lifetime ( 57.1 ns) was observed Smith, Brzozowski, et al., 1976 for J=4. See also Fink and Welge, 1964, Smith, 1969 whose low-resolution measurements gave τ(v=0) ~ 460 ns. Relative transition probabilities Lents, 1973.
12A(v=0,1) = -34.79; from Veseth, 1972 who gives also spin-spin and spin-rotation interaction constants. See also Horani, Rostas, et al., 1967, Bollmark, Kopp, et al., 1970.
13"True" rotational constants of Veseth, 1972; see also Horani, Rostas, et al., 1967, Bollmark, Kopp, et al., 1970. Λ-type doubling parameters may be found in Horani, Rostas, et al., 1967, Veseth, 1972. The effective constants Murai and Shimauchi, 1966 are Be = 16.6901, αe = 0.7440.
14Weak predissociation in v=0 and 1 above N=25 and 15, respectively, observed by high-resolution lifetime measurements Smith, Brzozowski, et al., 1976 and attributed to interaction with the unstable 5Σ- state arising from 4S + 2S.
15+9.9E-8J3(J+l)3 - 13E-12J4(J+l)4 Veseth, 1972; D1 = 17.85E-4, H1 = +6.0E-8 Veseth, 1972.
16Lifetime τ(v=0,N=4) = 404 ns Smith, Brzozowski, et al., 1976, first increasing to 453 ns at N=25, then decreasing rapidly to 96 ns at N=31 owing to predissociation. Similar results for v=1, see 14. Absorption oscillator strength 0.0076 Bennett and Dalby, 1960, Fink and Welge, 1964, Smith, 1969; f values in Harrington, Modica, et al., 1966 refer to emission and should be multiplied by 2 for comparison. Relative transition probabilities Lents, 1973.
17Undegraded 0-0 band.
18ωeze = -0.0353 (v≤9).
19Rotational constants from the analysis of the d→b bands [ Graham and Lew, 1978, 1≤ v"≤9]. Whittaker, 1968 gives Be = 16.7326 Whittaker, 1968 and αe = 0.6049 from the c→b 0-0 and 0-1 bands.
20He = 11E-8.
21Radiative lifetime τ=18 ms Zetzsch and Stuhl, 1975, Gelernt, Filseth, et al., 1975.
22Earlier theoretical predictions by Hurley, 1959 and Cade, 1968 gave 14200 and 13100 cm-1, respectively.
23From a comparison with ΔG(1/2) of ND.
24v00(b-X) + v00(c-b) - v00(c-a); in very good agreement with the singlet-triplet separation of 12500 cm-1 derived by Okabe, 1970 from the difference of the threshold energies for the production of NH(c 1Π) + C0(X 1Σ) or NH(X 3Σ) + CO(a 3Π) by photodissociation of HNCO. From the photoelectron spectrum of NH- Engleking and Lineberger, 1976 find 12735 ± 137 cm-1.
25"True" rotational constants of Veseth, 1972; spin-splitting constants γ = -0.0117, λ ~ +0.82. The evaluation of the constants by Veseth, 1972 takes fully into account the 3Π ~ 3Σ- interaction and thus leads to results which differ considerably from the effective constants of earlier investigators Dixon, 1959, Murai and Shimauchi, 1966, Bollmark, Kopp, et al., 1970, Malicet, Brion, et al., 1970. The latter are in good agreement with more precise constants obtained recently from the laser-magnetic-resonance spectrum Wayne and Radford, 1976 in v=0 and 1; Be = 16.6668, αe = 0.6470; γ(v=0) = -0.05466, γ(v=l)= -0.0517; 11(v=0,1) = +0.9198. See also Palmiere and Sink, 1976.
26D1 = 16.88E-4, H0 = 10.48E-8; H1 = +10.2E-8 Veseth, 1972.
27Rotation sp. 1
28From the limiting curve of dissociation in c 1Π Graham and Lew, 1978, see 7 and 5. Theoretical calculations by Liu and Verhaegen, 1970, Liu, Legentil, et al., 1972, Stevens, 1973 suggest D00 = 3.43, 3.31, 3.17 eV, respectively; the most recent prediction on theoretical and empirical grounds Meyer and Rosmus, 1975 is D00 = 3.40 eV. From the electron impact appearance potential of N2+ from HN3 Franklin, Dibeler, et al., 1958 follows D00 = 3.59 eV Franklin, Dibeler, et al., 1958; a shock-tube measurement Seal and Gaydon, 1966 gives D00= 3.21 eV. Both results are compatible with limits derived from the study of reactions of rare gas metastables with small NH-containing molecules Stedman, 1970, the upper limit being closer to the semi-empirical calculations of Companion and Ellison, 1960, Jordan and Longuet-Higgins, 1962, the lower limit being in better agreement with the thermochemical measurements of Kaskan and Nadler, 1972.
29Theoretical value Liu and Verhaegen, 1970; Foner and Hudson, 1966 give an electron impact appearance potential of 13.1 eV.
30By the laser-magnetic-resonance method; fine (see 25) and hyperfine structure constants.


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.

Cade and Huo, 1967
Cade, P.E.; Huo, W.M., Electronic structure of diatomic molecules. VI.A. Hartree-Fock wavefunctions and energy quantities for the ground states of the first-row hydrides, AH, J. Chem. Phys., 1967, 47, 614. [all data]

Das, Wahl, et al., 1974
Das, G.; Wahl, A.C.; Stevens, W.J., Ab initio study of the NH radical, J. Chem. Phys., 1974, 61, 433. [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]

Kouba and Ohrn, 1970
Kouba, J.; Ohrn, Y., Natural-orbital valence-shell CI studies of diatomic molecules. I. Potential-energy curves and spectra of imidogen, J. Chem. Phys., 1970, 52, 5387. [all data]

O'Neil and Schaefer, 1971
O'Neil, S.V.; Schaefer, H.F., III, Configuration interaction study of the X3Σ-, a1Δ, and b1Σ+ states of NH, J. Chem. Phys., 1971, 55, 394. [all data]

Hay and Dunning, 1976
Hay, P.J.; Dunning, T.H., Jr., Polarization Cl wavefunctions: the valence states of the NH radical, J. Chem. Phys., 1976, 64, 5077. [all data]

Narasimham and Krishnamurty, 1967
Narasimham, N.A.; Krishnamurty, G., The d1Σ+-c1Π system of NH, Proc. Indian Acad. Sci. Sect. A, 1967, 64, 97. [all data]

Whittaker, 1967
Whittaker, F.L., The Δv=0 sequence in the d1Σ+ - c1Π system of NH and ND, Proc. Phys. Soc. London, 1967, 90, 535. [all data]

Krishnamurty and Narasimham, 1969
Krishnamurty, G.; Narasimham, N.A., Predissociations in the d1Σ+-c1Π bands of NH, J. Mol. Spectrosc., 1969, 29, 410. [all data]

Whittaker, 1969
Whittaker, F.L., Observation of the d1Σ+ -b1Σ+ system of NH and ND in the vacuum ultraviolet, Can. J. Phys., 1969, 47, 1291. [all data]

Dieke and Blue, 1934
Dieke, G.H.; Blue, R.W., A1Π → 1Δ band of NH and the corresponding ND band, Phys. Rev., 1934, 45, 395. [all data]

Florent and Leach, 1952
Florent, R.; Leach, S., Contribution a l'etude du spectre d'emission de l'ammoniac et de l'ammoniac lourd: la transition 1Π→1Δ des radicaux NH et ND, J. Phys. Radium, 1952, 13, 377. [all data]

Funke, 1935
Funke, G.W., Die NH-banden bei λ3360, Z. Phys., 1935, 96, 787. [all data]

Murai and Shimauchi, 1966
Murai, T.; Shimauchi, M., Rotational distortions of 3Π states applied to NH molecule, Sci. Light (Tokyo), 1966, 15, 48. [all data]

Malicet, Brion, et al., 1970
Malicet, J.; Brion, J.; Guenebaut, H., Contribution a l'etude spectroscopique de la transition A(3Πi) - X(3Σ-) du radical NH, J. Chim. Phys. Phys.-Chim. Biol., 1970, 67, 25. [all data]

Gilles, Masanet, et al., 1974
Gilles, A.; Masanet, J.; Vermeil, C., Direct determination of the NH b1Σ+ → X3Σ- energy difference, Chem. Phys. Lett., 1974, 25, 346. [all data]

Radford and Litvak, 1975
Radford, H.E.; Litvak, M.M., Imine (NH) detected by laser magnetic resonance, Chem. Phys. Lett., 1975, 34, 561. [all data]

Wayne and Radford, 1976
Wayne, F.D.; Radford, H.E., The laser magnetic resonance spectra of imine (NH) and its isotopes, Mol. Phys., 1976, 32, 1407. [all data]

Rosengren and Pimentel, 1965
Rosengren, K.; Pimentel, G.C., Infrared Detection of Diimide, N2H2, and Imidogen, NH, by the Matrix Isolation Method, J. Chem. Phys., 1965, 43, 2, 507, . [all data]

Graham and Lew, 1978
Graham, W.R.M.; Lew, H., Spectra of the d1Σ+-c1Π and d1Σ+-b1Σ+ systems and dissociation energy of NH and ND, Can. J. Phys., 1978, 56, 85. [all data]

Smith, 1969
Smith, W.H., Lifetimes and total transition probabilities for NH, SiH, and SiD, J. Chem. Phys., 1969, 51, 520. [all data]

Smith and Liszt, 1971
Smith, W.H.; Liszt, H.S., Franck-Condon factors and absolute oscillator strengths for NH, SiH, S2 and SO, J. Quant. Spectrosc. Radiat. Transfer, 1971, 11, 45. [all data]

Rao and Lakshman, 1973
Rao, T.V.R.; Lakshman, S.V.J., True potential energy curves, r-centroids & Franck-Condon factors for d1Σ+-b1Σ+ system of NH molecule, Indian J. Pure Appl. Phys., 1973, 11, 539. [all data]

Smith, Brzozowski, et al., 1976
Smith, Wm.H.; Brzozowski, J.; Erman, P., Lifetime studies of the NH molecule: new predissociations, the dissociation energy, and interstellar diatomic recombination, J. Chem. Phys., 1976, 64, 4628. [all data]

Irwin and Dalby, 1965
Irwin, T.A.R.; Dalby, F.W., Experimental determination of the dipole moments of the degenerate states of NH, Can. J. Phys., 1965, 43, 1766. [all data]

Huo, 1968
Huo, W.M., Valence excited states of NH and CH and theoretical transition probabilities, J. Chem. Phys., 1968, 49, 1482. [all data]

Fink and Welge, 1964
Fink, E.; Welge, K.H., Lebensdauer der Elektronenzustande N2(C3Πu), N2+(B2Σu+), NH(A3Π), NH(c1Π), PH(3Π), Z. Naturforsch. A, 1964, 19, 1193. [all data]

Lents, 1973
Lents, J.M., An evaluation of molecular constants and transition probabilities for the NH free radical, J. Quant. Spectrosc. Radiat. Transfer, 1973, 13, 297. [all data]

Veseth, 1972
Veseth, I., Fine structure of 3Π and 3Σ- states in diatomic molecules, J. Phys. B:, 1972, 5, 229. [all data]

Horani, Rostas, et al., 1967
Horani, M.; Rostas, J.; Lefebvre-Brion, H., Find structure of 3Σ- and 3Π states of NH, OH+, PH, and SH+, Can. J. Phys., 1967, 45, 3319. [all data]

Bollmark, Kopp, et al., 1970
Bollmark, P.; Kopp, I.; Rydh, B., Rotational analysis of the ND A 3Πi-X3Σ- (0,0) band, J. Mol. Spectrosc., 1970, 34, 487. [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]

Harrington, Modica, et al., 1966
Harrington, J.A.; Modica, A.P.; Libby, D.R., A shock tube study of the NH(A3Π → X3Σ-) oscillator strengths, J. Quant. Spectrosc. Radiat. Transfer, 1966, 6, 799. [all data]

Whittaker, 1968
Whittaker, F.L., The c1Π-b1Σ+ band system of NH and ND, J. Phys. B:, 1968, 1, 977. [all data]

Zetzsch and Stuhl, 1975
Zetzsch, C.; Stuhl, F., Detection and quenching of NH(b1Σ+) in the pulsed vacuum UV photolysis of NH3, Chem. Phys. Lett., 1975, 33, 375. [all data]

Gelernt, Filseth, et al., 1975
Gelernt, B.; Filseth, S.V.; Carrington, T., Quenching and radiative lifetimes for NH(b1Σ+,v'=0), Chem. Phys. Lett., 1975, 36, 238. [all data]

Hurley, 1959
Hurley, A.C., The electronic structure of the first row hydrides BH, CH, NH, OH and FH. II. Excited states, Proc. R. Soc. London A, 1959, 249, 402. [all data]

Cade, 1968
Cade, P.E., Theoretical prediction of the singlet-triplet intercombination separations for NH, OH+, PH, and SH+, Can. J. Phys., 1968, 46, 1989. [all data]

Okabe, 1970
Okabe, H., J. Chem. Phys., 1970, 53, 3507. [all data]

Engleking and Lineberger, 1976
Engleking, P.C.; Lineberger, W.C., Laser photoelectron spectrometry of NH-: Electron affinity and intercombination energy difference in NH, J. Chem. Phys., 1976, 65, 4323. [all data]

Dixon, 1959
Dixon, R.N., The 0-0 and 1-0 bands of the A(3Πi)-X(3Σ-) system of NH, Can. J. Phys., 1959, 37, 1171. [all data]

Palmiere and Sink, 1976
Palmiere, P.; Sink, M.L., A Gaussian and Slater orbital study of fine structure in the X3Σ- and A3Π states of NH, OH+, PH, and SH+, J. Chem. Phys., 1976, 65, 3641. [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]

Liu, Legentil, et al., 1972
Liu, H.P.D.; Legentil, J.; Verhaegen, G., Calculated energy levels of some diatomic hydrides in Selected Topics in Molecular Physics [Proceedings of the national symposium at Ludwigsburg (Germany)], Clementi; Chemie GmbH, ed(s)., Weinheim, Bergstr., 1972, 19-33. [all data]

Stevens, 1973
Stevens, W.J., Ab initio determination of the dissociation energy of the X3Σ- state of imidogen, J. Chem. Phys., 1973, 58, 1264. [all data]

Franklin, Dibeler, et al., 1958
Franklin, J.L.; Dibeler, V.H.; Reese, R.M.; Krauss, M., Ionization and dissociation of hydrazoic acid and methyl azide by electron impact, J. Am. Chem. Soc., 1958, 80, 298. [all data]

Seal and Gaydon, 1966
Seal, K.E.; Gaydon, A.G., Shock-tube measurement of the dissociation energy of NH using absolute band intensities, Proc. Phys. Soc. London, 1966, 89, 459. [all data]

Stedman, 1970
Stedman, D.H., Reactions of Ar, Kr, and Xe metastables with simple NH-containing compounds, J. Chem. Phys., 1970, 52, 3966. [all data]

Companion and Ellison, 1960
Companion, A.L.; Ellison, F.O., Calculation of the dissociation energy of NH by a semiempirical interpolative method, J. Chem. Phys., 1960, 32, 1132. [all data]

Jordan and Longuet-Higgins, 1962
Jordan, P.C.H.; Longuet-Higgins, H.C., The lower electronic levels of the radicals CH, CH2, CH3, NH, NH2, BH, BH2 and BH3, Mol. Phys., 1962, 5, 121. [all data]

Kaskan and Nadler, 1972
Kaskan, W.E.; Nadler, M.P., Enthalpy of formation of NH, J. Chem. Phys., 1972, 56, 2220. [all data]

Foner and Hudson, 1966
Foner, S.N.; Hudson, R.L., Mass spectrometry of free radicals and vibronically excited molecules produced by pulsed electrical discharges, J. Chem. Phys., 1966, 45, 40. [all data]


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