Configuration interaction excited electronic states

Nesbet, R. K., Pyoc. Roy. Soc. London) A230, 312, 322, "Configuration interaction in orbital theories." "Excited electronic states of 1,3-butadiene."... 

The potential curves derived from such calculations can often be empirically improved by comparison with so-called experimental curves derived from observed spectroscopic data, using Rydberg-Klein-Rees (RKR) or other inversion procedures. It is often found, particularly for the atmospheric systems, that the remaining correlation errors in a configuration interaction (Cl) calculation are similar for many excited electronic states of the same symmetry or principal molecular-orbital description. Thus it is often possible to calibrate an entire family of calculated excited-state potential curves to near-spectroscopic accuracy. Such a procedure has been applied to the systems described here. 

Spin-Orbit Configuration Interaction Energies Applied to the Ground and Excited Electronic States of Thallium Hydride. 

To understand the zl-doubling in the A 1 IT v = 0 state of CS it is necessary to consider the spin-orbit interaction with other excited electronic states a very thorough analysis was presented by Field and Bergeman [12], The CS molecule possesses 22 electrons, of which the first 16 form an inner core which need not concern us further. Of the remaining six electrons, two occupy a a orbital (which we call la) and the remaining four occupy a n orbital, which we call lit. The lowest vacant orbital to be considered is a 3jt orbital. Consequently the electron configurations for the ground... 

The dominant electronic configuration for TiO in its X 3 A ground state may be written (core) (9a)1 (IS)1 where the 9a orbital is essentially the 4,v orbital of the Ti2+ ion and the IS orbital is essentially a 3d orbital of Ti2+. It is also necessary to provide wave functions for the low-lying excited electronic states of TiO because both the spin spin constant k and the A-doubling constant oA for the ground state depend upon mixing of excited states produced by a combination of the rotational and spin orbit interactions. Namiki, Saito, Robinson and Steimle [69] give an acceptable... 

Predictions can be made about the suitability of different system trajectories on the basis of orbital symmetry conservation rules (207). The most suitable trajectory is an approximation to the reaction path of the reaction under study. The rules can also yield information about the possible structure of the activated complex. The correlation diagram technique has been improved in a series of books by Epiotis et al. (214-216). The method is based on self-consistent field-configuration interaction or valence bond (SCF-CI or VB) (including ionic structures) wave functions. Applications on reactions in the ground states as well as in the excited electronic states are impressive however, the price to be paid for the predictions seems to be rather high. 

In this chapter, we discuss several approaches that have led from molecular entities to supramolecular soft and hard molecular architectures. Systems based on metal complexes with d and d electronic configuration forming assemblies such as micelles, vesicles, and gels, as well as crystalline structures, will be illustrated. The focus is on the role played by the metal complexes chemical structures as well as the choice of the intermolecular interactions in the ground and/or excited electronic states within the arrays. The selected examples, based on noncovalently linked luminescent systems, aim to the development of multifunctional assemblies, in which the self-organization generates new... 

Excited electronic states of l,6,6a2 -trithiapentalenes were calculated in order to explain the orange color of the compound which is not observed with carbocyclic 10 r-electron systems. Quantum chemical configuration interaction calculations using the AMI model and ab initio Hartree-... 

Relativistic and electron correlation effects play an important role in the electronic structure of molecules containing heavy elements (main group elements, transition metals, lanthanide and actinide complexes). It is therefore mandatory to account for them in quantum mechanical methods used in theoretical chemistry, when investigating for instance the properties of heavy atoms and molecules in their excited electronic states. In this chapter we introduce the present state-of-the-art ab initio spin-orbit configuration interaction methods for relativistic electronic structure calculations. These include the various types of relativistic effective core potentials in the scalar relativistic approximation, and several methods to treat electron correlation effects and spin-orbit coupling. We discuss a selection of recent applications on the spectroscopy of gas-phase molecules and on embedded molecules in a crystal enviromnent to outline the degree of maturity of quantum chemistry methods. This also illustrates the necessity for a strong interplay between theory and experiment. 

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