Spin-orbit coupling spectroscopic properties

As the actinides are a Second f series it is natural to expect similarities with the lanthanides in their magnetic and spectroscopic properties. However, while previous treatments of the lanthanides (p. 1242) provide a useful starting point in discussing the actinides, important differences are to be noted. Spin-orbit coupling is again strong (2000-4000 cm ) but, because of the greater exposure of the 5f... 

In this chapter, we therefore consider whether it is possible to eliminate spin-orbit coupling from four-component relativistic calculations. This is a situation quite different from that of more approximate relativistic methods where a considerable effort is required for the inclusion of spin-orbit coupling. We have previously shown that it is indeed possible to eliminate spin-orbit coupling from the calculation of spectroscopic constants [12,13]. In this chapter, we consider the extension of the previous result to the calculation of second-order electric and magnetic properties, i.e., linear response functions. Although the central question of this article may seem somewhat technical, it will be seen that its consideration throws considerable light on the fundamental interactions in molecular systems. We will even claim that four-component relativistic theory is the optimal framework for the understanding of such interactions since they are inherently relativistic. 

One of the most commonly employed procedures has been to simply extrapolate the molecular coupling from the available atomic parameters using the so-called atoms-in-molecules approach (72). Here (r,) is assumed to be constant for electrons with the same n and / quantum numbers. The values of are then assumed to be equal to the spin-orbit coupling constants n/, which are derived from atomic spectral data. This approach has been employed by Wadt (73) in all-electron studies, and by other groups (32,74) in effective potential calculations involving the rare-gas dimers and dimer ions. Ermler and co-workers used this approach coupled with AREP calculations to determine spectroscopic properties for various states of Au2 (42), Hg2, and HgTl (75). 

Spin-orbit coupling not only governs the amount and pattern of ZFS of the emitting triplet state, but it is also of dominant importance for the radiative emission decay rates and thus for the photoluminescence quantum yields. These properties are crucial for the suitability of triplet emitters in OLEDs. In conclusion, detailed spectroscopic studies of compounds triplet state properties in combination with... 

B. I. Schnieder and J. S. Cohen, Ground and Excited States of Ne2 and Ne . I. Potential Curves With and Without Spin-Orbit Coupling and Ground and Excited States of Ne2 and NeJ. II. Spectroscopic Properties and Radiative Lifetimes. Submitted to Journal of Chem. Phys. 

The spectroscopic and magnetic properties of actinoids are complicated and we mention them only briefly. Absorptions due to 5/-5/ transitions are weak, but they are somewhat broader and more intense (and considerably more dependent on the ligands present) than those due to 4f-4f transitions. The interpretation of electronic spectra is made difficult by the large spin-orbit coupling constants (about twice those of the lanthanoids) as a result of which the RusseU-Saunders coupling scheme partially breaks down. 

Gathering the experience of the previously discussed examples, we can say that the theoretical study of spectroscopic properties of transition metal complexes is far from being simple. Relativistic pseudopotentials (AREP and SOREP) were shown to be efficient and accurate tools to tackle this problem. From the methodological point of view, recently developed effective Hamiltonian SOCI methods that can treat correlation and spin-orbit coupling on the same footing exist (see section 2.2.5), and efforts have to be invested in applying... 

On the Efifects of Spin-Orbit Coupling on Molecular Properties Dipole Moment and Polarizability of PbO and Spectroscopic Constants for the Ground and Excited States... 

Having application codes available that can be used to calculate spectroscopic and structural properties of a range of electronic states of heavy-element-containing molecules and that treat electron correlation, spin-orbit coupling and other relativistic effects in a manner that allows for systematic improvements is invaluable to their detailed understanding. Accurate theoretical models of such systems... 

Whenever one wishes to investigate spectroscopic properties of lanthanide compounds one needs to include spin-orbit coupling in the calculations. Whereas for the AE DHF or DHFR calculations and subsequent Cl treatments it is necessary to work respectively in jj and COO) coupling for atoms and molecules, one has essentially three different choices at what stage of a PP calculation spin-orbit interaction is accounted for. 

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