Outer valence orbitals, ionization

Each cross section has a maximum around 13-16 eV, and the observed maxima shift to the higher energies with increasing the number of carbon atoms, i.e., from CH4 to -C4Hio, while the first ionization potentials shift to the lower energies as shown in Fig. 5. This shift of the maxima seems to be amenable to the trends in the ionization potentials of the deepest outer-valence orbitals of each molecule. 

Let us now consider the effect of a spectator vacancy on the Auger rate of the C, N, and O core hole in CH4, NH3, and H20 molecules, respectively. These molecules are isoelectronic with Ne however, the degeneracy of the outer valence orbitals is preserved only in the tetrahedral CH4. The Fano-ADC Auger widths of the singly core-ionized molecules [44] are presented in Table 6.4 alongside the available literature data. The calculated total Auger... 

Ionization of outer valence orbitals When an electron is removed from an orbital close to the highest occupied molecular orbital (HOMO), the spectrum is dominated by the contribution from only one solution of Eq. 1, since in that energy regime the self energy has no poles. 

Selected values of the adiabatic (ad) ionization potential of the outer-valence orbital Sa from different methods of measurement are given in order of increasing magnitude In the table below (PES = photoelectron spectroscopy, PIMS = photoionization mass spectrometry, also simulated by dipole (e, e+lon) spectroscopy, PA = photoabsorption). Other adiabatic and the vertical (vert) values for 5a and values for the other outer-valence orbital 2e are reported in separate sections on PES (also simulated by binary (e, 2e) spectroscopy) and MS work added to the table ... 

PES work yielded the following adiabatic and vertical ionization potentials for the outer-valence orbitals ... 

In addition to the main lines in the spectrum associated with the outer valence orbitals, the calculations predict interesting satellite structures as well as the appearance of multiple structure in the inner valence region. In the inner valence region a main line may cease to exist. Its intensity can be distributed over many ionic states, giving rise to the breakdown of the orbital picture of ionization. This phenomenon has been found to be common to most molecular systems. For a thorough discussion of this phenomenon we refer to Ref. 32. 

In this section, we present an overview of the photoabsorption cross section (o ) and the photoionization quantum yields (rh) for normal alkanes, C H2 +2 ( = 1 ), as a function of the incident photon energy in the vacuum ultraviolet range, and of the number of carbon atoms in the alkane molecule, because normal alkanes are typical polyatomic molecules of chemical interest. In Fig. 5, the vertical ionization potentials of the valence electrons, which interact with the vacuum ultraviolet photons, in each of these alkane molecules are indicated to show how the outer- and inner-valence orbitals associated with carbon 2p and 2s orbitals, respectively, locate in energy [7]. 

Table 13 Calculated (ADC(3)) energies (E, eV) and Intensities (P) of the outer- and Inner-valence orbital vertical Ionization transitions In thiophene ...

A complete analysis of the first and second row hydrides has been performed [13, 14], for both the cross section and asymmetry parameter profiles, from the outer valence to the deep core employing the KS method with the VWN exchange correlation potential and TS electron configuration. It is quite appealing that, due to the computational economy of the present method, it has been possible to compare the results of different systems with the same method, and therefore to identify precise trends along the series which are connected with the nature of the initial ionized orbital and to better understand how the continuum feels the different chemical environment. 

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