Vibronic spectra of the lower excited singlet states of styrene: A Time Dependent Density Functional Theory study

Franck–Condon simulations of the vibronic spectra of the styrene S1 and S2 states, based on geometries and force fields obtained with Time Dependent Density Functional Theory, are reported. Excellent agreement is obtained with experimentally observed vibrationally resolved excitation and emission spectra, allowing us to verify previous assignments and interpretations and, ultimately, to determine the changes in geometry and force field upon excitation. The influence of the choice of the exchange correlation functional on the calculated excitation energy, molecular geometry, and oscillator strength has been investigated and found to be less critical than what was conjectured from previous studies.