Molecular structure diatomic

The molecular and bulk properties of the halogens, as distinct from their atomic and nuclear properties, were summarized in Table 17.4 and have to some extent already been briefly discussed. The high volatility and relatively low enthalpy of vaporization reflect the diatomic molecular structure of these elements. In the solid state the molecules align to give a layer lattice p2 has two modifications (a low-temperature, a-form and a higher-temperature, yS-form) neither of which resembles the orthorhombic layer lattice of the isostructural CI2, Br2 and I2. The layer lattice is illustrated below for I2 the I-I distance of 271.5 pm is appreciably longer than in gaseous I2 (266.6 pm) and the closest interatomic approach between the molecules is 350 pm within the layer and 427 pm between layers (cf the van der Waals radius of 215 pm). These values are... 

Table 6.1 Details of homonuclear first-period diatomic molecular structures.

Group 17 one bond, giving diatomic molecular structures shown by all the halogens (see Topic F9). 

Examined in sufficient detail, the spectrum of every diatomic molecule is full of surprises. These surprises or perturbations can be at least as interesting as the vast expanses of textbook spectra lying between the surprises. Perturbations are more than spectroscopic esoterica. We hope that our discussion of perturbations provides a useful and unified view of diatomic molecular structure. This is a book about the spectra of diatomic molecules, warts and all. 

Herzberg G 1950 Molecular Spectra and Molecular Structure I Spectra of Diatomic Molecules (New York Van Nostrand-Reinhold)... 

Herzberg G 1989 Molecular Spectra and Molecular Structure. I. Spectra of Diatomic Molecules reprint (Malabar, FL Krieger)... 

K. P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure IV. Constant of Diatomic Molecules (Van Nostrand Reinhold Co., New York, 1979). 

Herzberg, G. and Huber, K. P. (1979) Molecular Spectra and Molecular Structure 4, in Constants of Diatomic Molecules, van Nostrand, Princeton, NJ,... 

Most values were taken from M. W. Chase, Jr., C. A. Davies, J. R. Downey, Jr.. D. J. Frurip, R. A. McDonald, and A. N. Syverud, "JANAF Thermochemical Tables, Third Edition", J. Phys. Chem. Ref. Data, 14, Supplement No. 1, 1985. A few (in parentheses) came from G. Hertzberg, Molecular Spectra and Molecular Structure, I. Spectra of Diatomic Molecules, and 11. In frared and Raman Spectra of Polyatomic Molecules, Van Nostrand Reinhold Co.. New York. 1950 and 1945. 

From the summary given by G. Herzberg, "Molecular Spectra and Molecular Structure. I. Diatomic Molecules," Prentice-Hall, Inc., New York, N. Y. 1939. 

Huber KP, Herzberg G (1979) Molecular spectra and molecular structure IV. Constants of diatomic molecules. Van Nostrand, New York... 

During the last decade MO-theory became by far the most well developed quantum mechanical method for numerical calculations on molecules. Small molecules, mainly diatomics, or highly symmetric structures were treated most accurately. Now applicability and limitations of the independent particle, or Hartree-Fock (H. F.), approximation in calculations of molecular properties are well understood. An impressive number of molecular calculations including electron correlation is available today. Around the equilibrium geometries of molecules, electron-pair theories were found to be the most economical for actual calculations of correlation effects ). Unfortunately, accurate calculations as mentioned above are beyond the present computational possibilities for larger molecular structures. Therefore approximations have to be introduced in the investigation of problems of chemical interest. Consequently the reliability of calculated results has to be checked carefully for every kind of application. Three types of approximations are of interest in connection with this article. 

We examine the derivation of information about molecular structure and properties from analysis of pure rotational and vibration-rotational spectral data of diatomic molecular species on the basis of Dunham s algebraic formalism, making comparison with results from alternative approaches. According to an implementation of computational spectrometry, wave-mechanical calculations of molecular electronic structure and properties have already played an important role in spectral reduction through interaction of quantum chemistry and spectral analysis. 

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