Relativistic Electronic Structure Theory for Molecular Spectroscopy

This review provides a concise introduction to relativistic electronic structure theory with a focus on the prediction of parameters relevant for molecular spectroscopy. For this purpose, a brief overview of wave-function-based electronic structure methods with a special focus on the calculation of electron correlation effects is given. These are essential for an accurate prediction of spectroscopic parameters from first-principles calculations. Then approximate relativistic Hamiltonians are discussed in detail regarding their accuracy and range of application. The a posteriori calculation of spin–orbit effects from correlated wave functions is briefly described and reviewed. The presentation concludes with an extensive discussion of calculated results for prototypical molecules. The focus is mainly on small molecules to which highly accurate relativistic methods can be applied and close agreement with experimental data can be achieved. Keywords: relativistic electronic structure theory; relativistic effects; relativistic Hamiltonians; spin–orbit coupling; molecular properties