Using the optimized 6-311G(d,p) geometry determined in question 1, perform the following equivalent core calculations for any two inequivalent carbons of butadiene:
(a) Equivalent core cation, for estimation of the core-ionized states. Predict the C 1s IP splitting (energy difference) for the two carbons and compare with the result from the ground state calculation performed in question 1. Compare the lowest energy unoccupied orbital energies for the two equivalent core calculations with each other and with the ground state calculation. Discuss and rationalize any observed changes.
(b) Equivalent core neutral, for estimation of the first core-excited state for C 1s excitation from the two selected carbon centres. Describe the two core-excited states in terms of the associated electronic transitions from the ground state of butadiene. From the computational results, predict the energy splitting between these two electronic transitions.