Jahn-Teller ethane radical cation

Figure 6.9. Top to bottom Two possible Jahn-Teller distorted geometries for the methane radical cation and calculated geometry for its energy minimum schematic representation of the SOMO for ethane radical cation SOMOs of three different propane radical cations observed by ESR the SOMO of butane radical cation and SOMOs for two conformers of pentane radical cation.

The ethane radical cation state sequence, X(2Eg) < A(2Ag) < B(2EU) < C(2AU), is well established from its repeatedly recorded PE spectrum3-5 (Figure 3). Both Jahn/Teller distortions of 0.7 eV and 0.8 eV, respectively, and the ionization into the predominantly ffcc-bonding M state A(2Ag) is located at about 13.4 eV in between them. 

FIGURE 3. (a) Comparison of the He(I) PE spectra of the >3d-symmetric molecules ethane and disilane, which exhibit Jahn/Teller splitting (J/T) of their M (e) states with dominant contributions ( ) to positive hole delocalization, based on their quantitative radical cation state assignment (see text), (b) United Atom correlation for the isoelectronic 18-electron species from Ar to SiFLj including the iso(valence)electronic 10-electron molecule CH4 with average atomic ionization energies... 

Fig. 1. a) Photoelectron spectroscopic radical cation state comparison of the electronically isovaient molecules disilane and ethane including Jahn-Teller splitting JT b) an approximate sequence of effective nuclear potentials for some main group element centers in heteroorganic molecules [2],... 

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