Low lying excitation energies

According to Eqs. (8) and (9), the g tensor of [4Fe-4S] clusters depends on four ferrous gi, 2, gi, gi) and two ferric gs,gs) local g tensors. This holds true even if the mixed-valence pair is fully delocalized Ca = Cb = i Owing to the low-lying excitation energies of the... 

A MODIFIED PARISER-PARR-POPLE FORMULATION FOR THE STUDY OF LOW LYING EXCITATION ENERGIES OF POLYENES... 

A modified Pariser-Parr-Pople formulation is described as a simpler approach to the study of polyene low lying excitation energies. The result of its application to polyenes of up to 20 carbon atoms is presented and compared with previous result obtained with double excitation configuration interaction. It is found that the proper ordering of the 2 Ag and i Bu excitation energies as well as other important characteristics revealed in previous studies are reproduced in this calculation. 

However, if the zeroth-order ground-state energy is well separated from low lying excited states, the diagonal... 

Simons J 1972 Energy-shift theory of low-lying excited electronic states of molecules J. Chem. Phys. 57 3787-92 A more recent overview of much of the EOM, Greens function, and propagator field is given in ... 

Use Configuration Interaction to predict the electronic spectra of molecules. The Configuration Interaction wave function computes a ground state plus low lying excited states. You can obtain electronic absorption frequencies from the differences between the energies of the ground state and the excited states. 

Singlet states with the same configuration as in Equation (7.59) with antiparallel spins of the electrons in the n 2p orbital are higher in energy and are low-lying excited states. 

With trinuclear clusters, we are now dealing with systems whose electronic structure depends on multiple intersite interactions that may differ from one iron pair to another. As a result, the separation between adjacent energy levels depends, not on the magnitude of these interactions, but on their difference. This may give rise to low-lying excited levels, which may have far-reaching effects on both the EPR spectrum and the relaxation properties. 

Since HF has a closed-shell electronic structure and no low-lying excited electronic states. HF-HF collisions may be treated quite adequately within the framework of the Born-Oppenheimer electronic adiabatic approximation. In this treatment (4) the electronic and coulombic energies for fixed nuclei provide a potential energy V for internuclear motion, and the collision dynamics is equivalent to a four-body problem. After removal of the center-of-mass coordinates, the Schroedinger equation becomes nine-dimensional. This nine-dimensional partial differential... 

For the latter two ions, the presence of low-lying excited states makes the inclusion of both the first-order contribution of the excited states and the second-order effects due to coupling of the ground / state with the excited states crucial in a correct estimation of the room-temperature values of xT. Indeed, second-order contribution in Van Vleck [9] expansion of the susceptibility is inversely proportional to the energy difference between the ground and the excited states ... 

TABLE 6. CASPT2 vertical excitation energies (eV) for the low-lying excited states of butadiene, hexatriene and octatetraene0... 

One important application of TDDFT is to compute low lying excited electronic states and energies. Simpler approaches, in which the virtual ground state Kohn-Sham orbitals and energies are determined as an estimate for excited states are often not sufficiently accurate for chemical applications and can only be used as a rather qualitative indication. 

The molecular ion will be of low symmetry and have an odd electron. It will have as many low-lying excited electronic states as necessary to form essentially a continuum. Radiationless transitions then will result in transfer of electronic energy into vibrational energy at times comparable to the periods of nuclear vibrations. 

These low-lying excited electronic states will in general not be repulsive hence, the molecular ions will not dissociate immediately, but rather remain together for a time sufficient for the excess electronic energy to become randomly distributed as vibrational energy over the ion. 

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