Chalcogens ionization energies

The group of the chalcogens sulfur, selenium and tellurium is a typical triad of the more electronegative nonmetals with relatively high-ionization energies, relatively strong element-element bonds and a clear tendency to form mono-and polyatomic anions (Table 1). 

Chalcogen Atomic radius (pm) Electronegativity" Ionization energy (kJ/mol)... 

Photoelectron spectroscopy has demonstrated that there is no linear correlation between the ionization energies and p values of azoles <84JHC269>. The gas phase photoelectron spectra of a series of hydantoin derivatives (32) have been compared with those of model compounds, and with the results of HAM/3 and CNDO/S calculations. Evidence is found for significant interactions between the 7r-orbitals and the chalcogen atoms for sulfur and selenium derivatives. In contrast, n-orbitals of the nitrogen atoms are localized in the whole series of compoimds, especially in the oxy analogues and in monosubstituted derivatives <88JST(175)447>. 

The Ch-related donor spectra differ on that point as several parity-forbidden transitions are observed. They start with symmetry-allowed transitions from the Is ground state to the valley-orbit split Is excited states, and are supplemented with 2s (T2) and 3s (T2) lines and Fano resonances within the photoionization spectrum. This is shown in Fig. 6.13 for Se°. Compared to group-V donors, this extends the energy span of the Ch°-related spectra to the ionization energy of the Is (T2) level (35-40 meV in isolated chalcogens) and it can even increase to 40-48 meV when singlet-triplet spin-forbidden transitions are observed. 

Spectra due to other Ch-related donor complexes in silicon have also been reported [118,243,262] and these complexes have been denoted ChcXn where index c represents complex and n = 2, 3, 4, and 5. The spectroscopic data of the ChcXi complexes and of SCX3 are already included in Tables 6.14 and 6.15. The spectra of the other complexes show only a few lines and their main characteristics are given in Table 6.20. Each chalcogen is given in order of decreasing ionization energies and a correlation between the indices and the atomic structure of the complexes has not been established. 

Table 6.20. 2p i — 2po spacings and ionization energies (meV) of ChcXi chalcogen complexes in silicon [262]... 

An evoked possibility of n-type doping of diamond with sulphur [219] has aroused an interest for the electronic properties of this element in diamond. It is now well established that, as expected from the properties of chalcogens in silicon and germanium, S behaves in diamond as a deep donor, with an ionization energy of 1 eV for S°, predicted from the ab initio DFT calculations [177]. However, the existence of S-related complexes with native defects or impurities like B is a possibility which could explain some appealing experimental results ([37], and references therein). 

Rationalize the trends in atomic radii, ionization energies, and electronegativities of the chalcogens on the basis of effective nuclear charges, atomic sizes, and so forth. 

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