Valence-excitation energy

The lowest vertical valence excitation energy for this cobalt cluster is 36.6 kcal/mol, which is a higher value than the exothermicity for dissociating Valence excited states will therefore not be available for dissociating either. The reason Co, is at all reactive towards Hg is that the d s atom can transform to a d s atom at a cost of 7.5 kcal/mol (see above). 

The lowest vertical valence excitation energy for Co is 29 kcal/mol, which means that valence excited states will not be available for dissociating H either. The alternative process for dissociating Hg for COg would be to change one of its d s atoms to d s, which only costs 8.8 kcal/mol but is an inner shell rearrangement process. 

Table 2 Singlet and triplet valence excitation energies in trans-...

Valence excitation energies for formaldehyde [36]. The second example is the GMC-QDPT calculation of valence excitation energies for formaldehyde molecule. Calculations on formaldehyde were carried out at the ground state experimental geometry (i.e. r(CO) = 1.203 A, r(CH) = 1.099 A, and 0(HCH) = 116.5°). The basis set used was Dunning s cc-pVTZ. 

Table 20.7 summarizes mean absolute errors in calculated excitation energies of five typical molecules by TDDFT. The table also displays calculated results of asymptotically corrected AC [79] and LB [78] (AC-BOP and LBOP) and hybrid B3LYP [72] functionals, which are mentioned in the former section. The ab initio SAC-Cl [103] results are also shown to confirm the accuracies. The 6-311G- -- -(2d,2p) basis set was used in TDDFT calculations [104,105]. As the table indicates, the LC scheme clearly improves Rydberg excitation energies that are underestimated for pure BOP functional, at the same (or better) level as the AC scheme does. It should be noted that LC and AC schemes also provide improvements on valence excitation energies for all molecules. LC and AC results are comparable to SAC-CI results. The LB scheme clearly modifies... 

Rydberg excitation energies, and however brings underestimations of valence excitation energies. B3LYP results are obviously worse than LC and AC results for both valence and Rydberg excitation energies. 

The descriptions of K-shell, L-shell, and valence electrons by the modified CV-B3LYP functional are assessed by calculating core- and valence-excitation energies... 

The use of hybrid functionals leads to systematically higher excitation energies. On average, this is an improvement over the GGA results, which are systematically too low. However, while diffuse excitations benefit from mixing in some exact exchange due to a reduction of the self-interaction error, valence excitation energies are not always improved, as is obvious for the and valence states. 

A typical x-ray photoelectron spectmm consists of a plot of the iatensity of photoelectrons as a function of electron E or Ej A sample is shown ia Figure 8 for Ag (21). In this spectmm, discrete photoelectron responses from the cote and valence electron energy levels of the Ag atoms ate observed. These electrons ate superimposed on a significant background from the Bremsstrahlung radiation inherent ia n onm on ochrom a tic x-ray sources (see below) which produces an increa sing number of photoelectrons as decreases. Also observed ia the spectmm ate lines due to x-ray excited Auger electrons. 

Quantum effects are observed in the Raman spectra of SWCNTs through the resonant Raman enhancement process, which is seen experimentally by measuring the Raman spectra at a number of laser excitation energies. Resonant enhancement in the Raman scattering intensity from CNTs occurs when the laser excitation energy corresponds to an electronic transition between the sharp features (i.e., (E - ,)" type singularities at energy ,) in the ID electronic DOS of the valence and conduction bands of the carbon CNT. 

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... 

Vertical excitation energies to states of B symmetry, calculated at the level using the orbitals optimized for the neutral molecule with the MCSCF/6422 expansion, are reported Table 12. The I Bi valence state and 2 B (3p) Rydberg state of C3H2 are respectively 5.2 eV and 7.5 eV above the ground state with large transition moments of... 

An obvious remedy to this situation is to use potentials that by construction exhibit the correct asymptotic behavior. Indeed, using the LB94 or the HCTH(AC) potentials yields significantly improved Rydberg excitation energies. As an instructive example, we quote the detailed study by Handy and Tozer, 1999, on the benzene molecule. These authors computed a number of singlet and triplet n->n valence and n —> n = 3 Rydberg excitations... 

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