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Potassium sodide

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 23Na39K
E 25228 1 95.85 H 0.94        E larrow X R 25214 H
Sinha, 1948
D (1Pi) 20090.6 82.17 H 0.350 -.00814       D larrow X R 20070.0 H
Loomis and Arvin, 1934; missing citation
C 1Pi 16993.8 71.33 Z 1.236 2 8.8E-3 0.05744 0.000078 3  32.1E-7 4  4.505 C larrow X R 16967.2 Z
Loomis and Arvin, 1934; missing citation; Allegrini, Moi, et al., 1977
A (1Sigma+) 12139.7 79.852 H 0.0872 -3.89E-3 5      A larrow X R 12118.0 H
Loomis and Arvin, 1934
X 1Sigma+ 0 124.134 Z 0.511 6  0.0905 0.0004584 7  8.19E-7 4  3.589 8  
Dagdigian and Wharton, 1972
magn. reson. 9
missing citation
Note: It now appears that the ground state constants of Toueg, 1974 are unreliable; the uncertainty also affects the new results for the C state Allegrini, Moi, et al., 1977 [Arimondo, private comm. 1978]


1Recalculated; Sinha, 1948 gives 25201 which must be erroneous.
2omegaeze = -0.000223. All constants obtained from a study of the C state vibrational-rotational structure by laser excitation and collision-induced dissociation Allegrini, Moi, et al., 1977. Similar vibrational constants have been derived by Loomis and Arvin, 1934 from absorption and magnetic rotation spectra; convergence limit at 18025 ± 250 cm-1 above X 1Sigma+(v=0), corresponding to Na(2S) + K(4p 2P).
3missing note
4Centrifuga1 distortion constants as given by Allegrini, Moi, et al., 1977 and Toueg, 1974; there is no agreement with De values calculated from 4Be3/omegae2.
5Perturbations (possibly by a 3Pi state) are very likely the cause for the appearance of a weak magnetic rotation spectrum.
6omegaexe= -7.9E-5(v+1/2)3 - 2.47E-7(v+1/2)4 - 2.50E-7(v+1/2)5 Toueg, 1974.
7alphav= -9.4E-7(v+1/2)2 - 9.08E-8(v+1/2)3 Toueg, 1974.
8Mol. beam re electric 12
9gJ = -0.0253 muN Brooks, Anderson, et al., 1972. For an NMR experiment using-optical pumping see Konig and Weber, 1976.
10Extrapolation of the vibrational levels in C 1Pi assuming that this state has no potential maximum.
11Photoionization appearance potential Foster, Leckenby, et al., 1969.
12muel(v=0) = 2.667 D [recalculated from mu02/B0 = 3.966E-19 cm3 Dagdigian and Wharton, 1972 with the new value for B0]. Electric quadrupole coupling constants Dagdigian and Wharton, 1972; see also Brooks, Anderson, et al., 1972.


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

Sinha, 1948
Sinha, S.P., Ultra-violet bands of NaK, Proc. Phys. Soc. London, 1948, 60, 447. [all data]

Loomis and Arvin, 1934
Loomis, F.W.; Arvin, M.J., The band spectrum of NaK, Phys. Rev., 1934, 46, 286. [all data]

Allegrini, Moi, et al., 1977
Allegrini, M.; Moi, L.; Armondo, E., Investigation of C1«PI» state in NaK molecules by laser excitation and collision-induced dissociation, Chem. Phys. Lett., 1977, 45, 245. [all data]

Dagdigian and Wharton, 1972
Dagdigian, P.J.; Wharton, L., Molecular beam electric deflection and resonance spectroscopy of the heteronuclear alkali dimers: 39K7Li, Rb7Li, 39K23Na, Rb23Na, and 133Cs23Na, J. Chem. Phys., 1972, 57, 1487. [all data]

Toueg, 1974
Toueg, Thesis, quoted by Allegrini, Moi, et al., 1977, University of Columbia, 1974, 1. [all data]

Brooks, Anderson, et al., 1972
Brooks, R.A.; Anderson, C.H.; Ramsey, N.F., Molecular beam experiments on KNa and LiNa, J. Chem. Phys., 1972, 56, 5193. [all data]

Konig and Weber, 1976
Konig, F.; Weber, H.G., NMR in Na2 and NaK by optical pumping, Chem. Phys. Lett., 1976, 44, 293. [all data]

Foster, Leckenby, et al., 1969
Foster, P.J.; Leckenby, R.E.; Robbins, E.J., The ionization potentials of clustered alkali metal atoms, J. Phys. B:, 1969, 2, 478. [all data]


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