Mechanisms of photoexcitation and photoionization in small water clusters.

The mechanisms of photoexcitation and photoionization in small water clusters in gas phase, (HO) ; = 2-3, are studied using the complete active-space second-order perturbation theory (CASPT2) with the aug-cc-pVDZ basis set. The present study characterizes for the first time the structures and energetics of common transition and intermediate complexes in the photoexcitation and photoionization mechanisms in the lowest singlet-excited state. The results showed that the photoexcitation of the water monomer by a single photon can directly generate [OH]˙ and [H]˙ in their respective electronic-ground states, and a single photon with approximately the same energy can similarly lead to the photoexcitation and also to the photoionization in the water clusters.

Substitution pattern on anthrol carbaldehydes: excited state intramolecular proton transfer (ESIPT) with a lack of phototautomer fluorescence.

Photophysical properties and excited state intramolecular proton transfer (ESIPT) reactivity for anthrol carbaldehydes 1-5 have been investigated computationally and experimentally by steady-state and time-resolved fluorescence and laser flash photolysis (LFP). 1,2-Disubstituted anthrol carbaldehydes 1 and 2 are not ESIPT reactive, contrary to naphthol analogues. The main deactivation channels from S for 1 and 2 are fluorescence (Φ = 0.

Exploration of Excited State Deactivation Pathways of Adenine Monohydrates.

Binding of a single water molecule has a dramatic effect on the excited state lifetime of adenine. Here we report a joint nonadiabatic dynamics and reaction paths study aimed at understanding the sub-100 fs lifetime of adenine in the monohydrates. Our nonadiabatic dynamics simulations, performed using the ADC(2) electronic structure method, show a shortening of the excited state lifetime in the monohydrates with respect to bare adenine.

Timescales of N-H bond dissociation in pyrrole: a nonadiabatic dynamics study.

The excitation wavelength dependent photodynamics of pyrrole are investigated by nonadiabatic trajectory-surface-hopping dynamics simulations based on time dependent density functional theory (TDDFT) and the algebraic diagrammatic construction method to the second order (ADC(2)). The ADC(2) results confirm that the N-H bond dissociation occurring upon excitation at the origin of the first excited state, S1(πσ*), is driven by tunnelling [Roberts et al., Faraday Discuss.

Dynamics and mechanism of structural diffusion in linear hydrogen bond.

Dynamics and mechanism of proton transfer in a protonated hydrogen bond (H-bond) chain were studied, using the CH(3)OH(2)(+)(CH(3)OH)(n) complexes, n = 1-4, as model systems. The present investigations used B3LYP/TZVP calculations and Born-Oppenheimer MD (BOMD) simulations at 350 K to obtain characteristic H-bond structures, energetic and IR spectra of the transferring protons in the gas phase and continuum liquid. The static and dynamic results were compared with the H(3)O(+)(H(2)O)(n) and CH(3)OH(2)(+)(H(2)O)(n) complexes, n = 1-4.