The current volume in the series, Vibrational Spectra and Structure, is a single topic volume on gas phase structural parameters. The title of the volume, Equilibrium Structural Parameters, covers the two most common techniques for obtaining gas phase structural parameters: microwave spectroscopy and the electron diffraction technique. Since the quantum chemical method provides equilibrium geometries, the volume is an attempt to provide a connection between the experimental and theoretical parameters. The book provides a review on molecular structure determinations from spectroscopic data using scaled moments of inertia. The limited number of molecules for which equilibrium parameters have been obtained and the requirement of a large number of microwave data needed to obtain the equilibrium structural parameters is noted. Electron diffraction technique is reviewed, along with a description of how this can incorporate structural information from microwave spectroscopy, vibrational spectroscopy, or theoretical calculations to improve the determination of the structural parameters by electron diffraction studies. Also discussed are the theory and methods of microwave spectroscopy, describing in some detail ro and rs structures as well as rm structures and corrections based on ab initio calculations. The accuracy of the molecular geometry predictions by quantum chemical methods is considered in some detail with data presented in graphic rather than tabular form. This makes it possible to readily note the difference in the parameters predicted at the various levels of quantum mechanical calculations. The four authors have provided a coherent description of the various structural parameters obtained experimentally along with treatments needed to extract equilibrium bond distances and angles.
Preface to the series. Preface to Volume 24. Contributors to Volume 24. Contents of other Volumes. Molecular Structure Determination from Spectroscopic Data using Scaled Moments of Inertia (M.D. Harmony). Introduction. Review of Basics. Molecular Structure Methods. r0 and re structures. rs structures. rm structures. Miscellaneous methods. rрm structures. Equilibrium structures of polyatomic organic molecules. Some pivotal observations. rрm heavy-atom structures. rрm structures of hydrogen-containing molecules. rрm applications. Conclusion. Acknowledgments. References. Electron Diffraction: A Combination with Other Techniques (V.S. Mastryukov). Introduction. The Electron Diffraction Technique. Experimental equipment. Basic relations. Structure analysis. Combined Application of Experimental Techniques. Supersonic nozzle. Mass spectrometer. Laser. Techniques Incorporated in Structural Analysis. Vibrational spectroscopy. Rotational constants. Theoretical calculations. Liquid crystal NMR spectroscopy. Concluding Remarks and Acknowledgements. References. The Quest for the Equilibrium Structure of Molecules (P. Groner). Introduction. Theory and Methods. Vibration-rotation interactions. re stuctures. Traditional rs method. Least-squares methods. r0 and rs structures. rm structures and beyond. Corrections based on ab initio calculations. Other methods. Molecular Structures from Spectroscopy Since 1980. Introduction to tables 2-6. Selected examples. Conclusion. Acknowledgment. References. The Accuracy of Molecular Geometry Predictions by Quantum Chemical Methods (S. Bell). Introduction. Computational Methods. Presentation of Results. Small Molecules. Bond lengths. Bond angles. Hydrocarbons. C-C single bonds lengths in alkanes and alkyl moieties. C-C bonds adjacent to C=C, C≡C, oxygen and fluorine atoms. C=C double bonds lengths. C≡C triple bonds lengths. C-H bond lengths. Bond angles in hydrocarbons. Molecules Containing Nitrogen, Oxygen or Fluorine. CN, C-O and C-F bond lengths. C=O bond lengths and associated bond angles. Molecules with central oxygen atoms. Torsional Angles. Conclusions. Author index. Subject index.
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