Vertical ionization energies

FIGURE 6. Schematic representation of the PE spectrum of a hypothetical molecule. Abscissa Ionization energy / in eV. Ordinate Intensity C in counts per second (cps). Pj = adiabatic ionization energy, / = vertical ionization energy, I f = ionization energy corresponding to the maximum of the band... 

Table 24 Vertical Ionization Energies (eV) of rr-Molecular Orbitals of Parent Heterocycles...

Experimental and calculated (CNDO/S) vertical ionization energies have been measured for pyrazol-3-ine-5-thiones (108 R = H, Me). These compounds exhibit an intense low-energy band (7.55-7.60 eV) corresponding to the ionization of both a thiocarbonyl tt-electron and the sulfur n electron (78JA1275). 

Table 3 Vertical Ionization Energies for some Thiiranes and Thiirenes...

In this section we will consider how the periodic table can be used to correlate properties on an atomic scale. In particular, we will see how atomic radius, ionic radius, ionization energy, and electronegativity vary horizontally and vertically in the periodic table. 

Fig. 9. Sketch of potential energy curves of a segment of conducting polymers in the ground state and in the ionized state Eip, is the vertical ionization energy, E ] the relaxation energy gained in the ionized state, Eip d the ionization energy of the distorted molecule, and Ej, the geometrical distortion energy in the ground state...

The Brueckner-reference method discussed in Section 5.2 and the cc-pvqz basis set without g functions were applied to the vertical ionization energies of ozone [27]. Errors in the results of Table IV lie between 0.07 and 0.17 eV pole strengths (P) displayed beside the ionization energies are approximately equal to 0.9. Examination of cluster amplitudes amd elements of U vectors for each ionization energy reveals the reasons for the success of the present calculations. The cluster operator amplitude for the double excitation to 2bj from la is approximately 0.19. For each final state, the most important operator pertains to an occupied spin-orbital in the reference determinant, but there are significant coefficients for 2h-p operators. For the A2 case, a balanced description of ground state correlation requires inclusion of a 2p-h operator as well. The 2bi orbital s creation or annihilation operator is present in each of the 2h-p and 2p-h operators listed in Table IV. Pole strengths are approximately equal to the square of the principal h operator coefiScient and contributions by other h operators are relatively small. 

Summary Organosilicon compounds, especially those containing numerous bulky (H3C)3Si substituents, show structural distortions, hindered dynamics, and unusual molecular properties such as record low first vertical ionization energies or extreme spin and charge delocalization. 

The vertical first ionization energies of (R3Si)3Si-Si(SiR3)3 as well as of (R3Si)3Si-C6H4-Si(SiR3) are each the lowest ones known for the respective type of compounds [5a-c],... 

Vertical ionization energies of the two highest molecular orbitals and of orbitals mainly localized on the substituent of a-substituted derivatives of furans, thiophenes, selenophenes, and tellurophenes have been determined.25 Assignments of some of the bands other than the first two in the photoelectron spectra of tellurophene and selenophene are proposed, and the effect of the ring on the orbitals mainly localized on the substituent is briefly discussed. 

FIGURE 8. Regression of observed vertical ionization energies /" on the corresponding HMO xj values for the set of planar polyenes listed in Table 2... 

Table 3.5. Adiabatic and vertical ionization energies of small molecules (cf. Table 3.4), compared with Koopmans -theorem (KT) estimates using MO or NBO orbital energies, and with experimental adiabatic values...

Tab. 4.4 Vertical and adiabatic ionization energies (kcal mol-1) for a set of furocoumarins and related compounds, in vacuum and in bulk water solvent. 1 eV=23.06 kcal mol-1.

Using the fact that the energy is linear with respect to the number of electrons and Janak s theorem [31], the orbital energies of the N—n and N+n electron system become equal to the exact ground state vertical ionization energy and electron affinity, respectively ... 

Figure 4.2 Potential energy curves for the molecules AB and AB+ showing the vertical and the adiabatic ionization energies of AB. r is the A-B bond length, and v represents the vibrational quantum number.

Tables 5.2 and 5.3 display vertical ionization energies of the two tautomers (keto and enol) with the lowest energies. The keto form is shown in Fig. 5.1. In the enol form, a proton is transferred from nitrogen 1 to the oxygen atom. P3 ionization energies for both isomers are close to the lowest peak in the photoelectron spectrum (PES) [44],...

Our implementation computes only vertical ionization energies and electron affinities, but experimental results for the G2 species are adiabatic. To facilitate a direct comparison between the theoretical and experimental results, it is necessary that either the theoretical results be corrected to adiabatic values or that the adiabatic values be related to vertical ones. We have chosen the latter approach and have corrected the experimental results with computational data. 

Transition energies between cations and neutral species were calculated by two procedures. In the first one, the vertical ionization energy of the neutral molecule was determined with the P3 method. These values were compared with experimental adiabatic ionization energies of the neutral molecules, which were adjusted according to... 

---