Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy J. Chem. Phys. 135, 194307 (2011) Population inversion of molecular nitrogen in an Ar: N2 mixture by selective resonance-enhanced multiphoton ionization J. Appl. Phys. 110, 083112 (2011) Control of vibronic excitation using quantum-correlated photons J. Chem. Phys. 135, 164304 (2011) Resonant two-photon ionization spectroscopy of jet-cooled PdSi J. Chem. Phys. 135, 134308 (2011) Optical purification of a mixture of chiral forms by dimer formation J. Chem. Phys. 135, 124304 (2011) Additional information on J. Chem. Phys. In this study, the one-and two-photon absorption spectra of seven azoaromatic compounds ͑five pseudostilbenes-type and two aminoazobenzenes͒ were theoretically investigated using the density functional theory combined with the response functions formalism. The equilibrium molecular structure of each compound was obtained at three different levels of theory: Hartree-Fock, density functional theory ͑DFT͒, and Møller-Plesset 2. The effect of solvent on the equilibrium structure and the electronic transitions of the compounds were investigated using the polarizable continuum model. For the one-photon absorption, the allowed → ‫ء‬ transition energy showed to be dependent on the molecular structures and the effect of solvent, while the n → ‫ء‬ and → ‫ء‬ ͑n͒ transition energies exhibited only a slight dependence. An inversion between the bands corresponding to the → ‫ء‬ and n → ‫ء‬ states due to the effect of solvent was observed for the pseudostilbene-type compounds. To characterize the allowed two-photon absorption transitions for azoaromatic compounds, the response functions formalism combined with DFT using the hybrid B3LYP and PBE0 functionals and the long-range corrected CAM-B3LYP functional was employed. The theoretical results support the previous findings based on the three-state model. The model takes into account the ground and two electronic excited states and has already been used to describe and interpret the two-photon absorption spectrum of azoaromatic compounds. The highest energy two-photon allowed transition for the pseudostilbene-type compounds shows to be more effectively affected ͑ϳ20%͒ by the torsion of the molecular structure than the lowest allowed transition ͑ϳ10%͒. In order to elucidate the effect of the solvent on the two-photon absorption spectra, the lowest allowed two-photon transition ͑dipolar transition͒ for each compound was analyzed using a two-state approximation and the polarizable continuum model. The results obtained reveal that the effect of solvent increases drastically the two-photon cross-section of the dipolar transition of the pseudostilbene-type compounds. In general, the features of both one-and two-photon absorption spectra of the azoaromatic compounds are well reproduced by the theoretical calculations.

In this work, we investigate the control of the two-photon absorption process of a series of organic compounds via spectral phase modulation of the excitation pulse. We analyzed the effect of the pulse central wavelength on the control of the two-photon absorption process for each compound. Depending on the molecules' two-photon absorption position relative to the excitation pulse wavelength, different levels of coherent control were observed. By simulating the two-photon transition probability in molecular systems, taking into account the band structure and its positions, we could explain the experimental results trends. We observed that the intrapulse coherent interference plays an important role in the nonlinear process control besides just the pulse intensity modulation.