Electronic structure calculations vertical ionization energy

For closer elaboration of the numerous radical cation states of molecules on energy and time scales (Figure 2a and c), photoelectron (PES)3,5,16 and electron spin resonance (ESR/ENDOR)10,25 spectroscopic techniques have complementary time ranges Vertical ionization energy patterns are measured with a time resolution of less than 10 15 s (Figure 2c) without any vibrational structural changes on electron ejection and can therefore be correlated to the eigenvalues calculated for the neutral molecule by... 

Bouma, Poppinger and Radom" made a detailed analysis of the possible structures of the ions of n- and isobutane (among other hydrocarbons) using ab initio calculations of different levels. They reviewed also older calculations. The HOMO orbital of n-butane is the 7ag[C2h] orbital. It is sufficiently separated from the next lower MO, such that one can assume that the electron is eliminated from the HOMO. The corresponding ionized state does not correspond to a minimum and the authors calculate a difference between the vertical and the adiabatic ionization energy of 1.0 eV, compared with an experimentally determined value of The HOMO of n-butane includes... 

---