Accurate Determination of Electric Field Gradients for Heavy Atoms and Molecules

Accurate Determination of Electric Field Gradients for Heavy Atoms and Molecules 

An overview of relativistic state-of-the-art calculations on electric field gradients (EFG) in atoms and molecules neccessary for the determination of nuclear quadrupole moments (NQM) is presented. Especially for heavy elements four-component calculations are the method of choice due to the strong weighting of the core region by the EFG operator and the concomitant importance of relativity. Accurate nuclear data are required for testing and verification of the various nuclear models in theoretical nuclear physics and this field represents an illustrative example of how electronic structure theory and theoretical physics can fruitfully interplay. Basic atomic and molecular experimental techniques for the determination of the magnetic and electric hyperfine constants A and B axe briefly discussed in order to provide the reader with some background information in this field. 

The phenomenon of hyperfine structure has been well-known since the early days of spectroscopic experiments. At the very beginning hyperfine effects were attributed to the occurrence of different isotopes in the substances measured. This explanation soon had to be replaced due to the fact that the measured line spacings substantially exceeded 

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M. Pempointner Accurate Determination of Electric Field Gradients for Heavy Atoms and Molecules in Theoretical and Computational Chemistry, Chapter 5 in this book. 

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