https://www.selleckchem.com/products/arq531.html A theoretical study of the K-shell total photoabsorption and photoionization cross section spectra of water and ammonia bonded to benzene (C6H6) and the polycyclic aromatic hydrocarbons (PAHs) naphthalene (C10H8), coronene (C24H12) and circumcoronene (C54H18) by van der Waals (vdW) forces is presented. The discretized electronic pseudospectra at the oxygen and nitrogen K-edges, covering the discrete and the continuum spectral regions, were obtained at the time-dependent density functional theory (TDDFT) level with dispersion correction. An analytic continuation procedure based on the Padé approximants was used in order to obtain the K-shell cross sections of the structures at the discrete and the continuum regions of the spectra. By examining the electronic spectra of water and ammonia bonded to coronene and circumcoronene, we observed that our results agree well with the experiments performed with graphene. This work provides a quantum mechanical interpretation to the NEXAFS experiments of water and ammonia adsorbed on graphene in terms of a physisorption model of these molecules by van der Waals forces.Photoinduced ring-opening, decay, and isomerization of spirobenzopyran have been explored by the OM2/MRCI nonadiabatic dynamics simulations based on Tully's fewest-switches surface hopping scheme. The efficient S1 to S0 internal conversion as observed in experiments is attributed to the existence of two efficient excited-state decay pathways. The first one is related to the C-N dissociation, and the second one is done to the C-O dissociation. The C-O dissociation pathway is dominant, and more than 90% trajectories decay to the S0 state via the C-O bond-fission related S1/S0 conical intersections. Near these regions in the S0 state, trajectories can either return to spirobenzopyran or proceed to various intermediates including merocyanine via a series of bond rotations. Our nonadiabatic dynamics simulations also demons