I would like to know what is the excitation amplitude as a result of TDDFT calculation for electronic excitations. Higher the values favourable in what character in electron transitions..?
Using the TDDFT method installed in G09 you can get the excitation coefficient for each of the excitation in the molecule. For closed shell systems, the square of this coefficient times 100 gives the percentage contribution of that excitation. Thus the larger the coefficient is the higher is the excitation contribution.
Please note, that for open shell systems the calculation for the excitation contribution is different from those of the closed shell systems.