The role of distributed atomic point charges and polarizabilities of solvent molecules on one- and two-photon absorption spectra of aqueous p-nitroaniline

In this work, we demonstrated the electrostatic and polarization effects created from distributed atomic point charges and polarizabilities of solvent molecules, respectively, when calculating optical response properties of solution-phase molecule within the context of the discrete solvent reaction field. Aqueous p-nitroaniline molecule was selected as the model system for our research purpose. One- and two-photon absorption spectra were constructed by carrying out the damped response theory calculations within time-dependent density functional theory. As compared to the full treatment, we investigated different effects of electrostatics and polarizations on spectral parameters of interest. Our calculations showed that the larger contributions to the calculated red shift in excitation energy was from electrostatic term, but polarization contribution was comparable in magnitude. On the other hand, electrostatic term was the principal feature for absorption strength and spectral width.