Time-dependent density functional theory calculations of photoabsorption spectra in the vacuum ultraviolet region

The results of time-dependent density functional theory (TD-DFT) calculatio ns of the transition energies and oscillator strengths of the excited state s of formaldehyde, benzene, ethylene, and:methane are reported. The local D FT (LDFT) transition energies tend to be smaller than experimental values b y 0.1-1.3 eV. Inclusion of nonlocal (NLDFT) (gradient corrected) effects ma de the calculated energies larger than the LDFT values and thus made the en ergies closer to the experimental values for formaldehyde, ethylene, and me thane. For benzene, no significant change in the calculated transition ener gies due to the addition of nonlocal effects was observed. The TD-DFT oscil lator strengths are much better than those found at the configuration inter action singles (CIS) level. The agreement between the calculated TD-DFT val ues and the experimental values for the oscillator strengths is quite good, at least semiquantitative at both the LDFT and NLDFT levels.