A photosynthetic organism is subjected to photo-oxidative stress when more light energy is absorbed than is used in photosynthesis. In the light, highly reactive singlet oxygen can be produced via triplet chlorophyll formation in the reaction centre of photosystem II and in the antenna system. In the antenna, triplet chlorophyll is produced directly by excited singlet chlorophyll, while in the ...

We report the synthesis and the photophysical properties of UV light-harvesting arrays constructed around a [Ru(bpy)3] core (bpy ) 2,2′-bipyridine) bearing one and three pyrenyl units in the periphery. The free ligand containing the pyrenyl unit, 4-methyl-4′-(2-hydroxyethylpyrenyl)-2,2′-bipyridine, displays an intense emission band centered near 400 nm with a lifetime of 264 ns, characteristic ...

The peridinin chlorophyll-a protein (PCP) is a water-soluble, trimeric light harvesting complex found in marine dinoflagellates that binds peridinin and Chl-a in an unusual stoichiometric ratio of 4:1. In this paper, the pathways of excited-state energy transfer and relaxation in PCP were identified by means of femtosecond visible-pump, mid-infrared probe spectroscopy. In addition, excited-stat...

Two different approaches to increase intersystem crossing rates in polymethine-like molecules are presented: traditional heavy-atom substitution and molecular levels engineering. Linear and nonlinear optical properties of a series of polymethine dyes with Br- and Se-atom substitution, and a series of new squaraine molecules, where one or two oxygen atoms in a squaraine bridge are replaced with ...

We address a recent theoretical discrepancy concerning the Kondo effect in quantum dots with an even number of electrons where spin-singlet and -triplet states are nearly degenerate. We show that the discrepancy arises from the fact that the Kondo scaling involves many parameters, which makes the results depend on concrete microscopic models. We illustrate this by the scaling calculations of th...

We investigate two serially aligned quantum dots in the molecular regime of large tunnel couplings t . A Zeeman field B is used to tune the energy difference of singlet and triplet spin configurations. Attaching this geometry to BCS source and drain leads with gap and phase difference φ gives rise to an equilibrium supercurrent J . To compute J in the presence of Coulomb interactions U between ...

Correlated electronic structure calculations at single and multireference levels of theory have been carried out for several neutral and radical anion electronic states of 2,3-didehydro-1,4-benzoquinone, a quinone analog of o-benzyne. The molecule is predicted to be a ground-state singlet (1A1) with a 298 K heat of formation of 200.6 kJ mol , a heat of hydrogenation (1 equiv.) of 323.5 kJ mol ,...

We study the photoluminescence spectrum of a low-density (nu<1) two-dimensional electron gas at high magnetic fields and low temperatures. We find that the spectrum in the fractional quantum Hall regime can be understood in terms of singlet and triplet charged excitons. We show that these spectral lines are sensitive probes for the electron compressibility. We identify the dark triplet charged ...

Few-electron quantum dots are investigated in the regime of strong tunneling to the leads. Inelastic cotunneling is used to measure the two-electron singlet-triplet splitting above and below a magnetic field driven singlet-triplet transition. Evidence for a nonequilibrium two-electron singlet-triplet Kondo effect is presented. Cotunneling allows orbital correlations and parameters characterizin...

Conformational dependence of spin-orbit coupling (SOC) in flexible Paternò-Büchi (PB) diradicals has been studied with high-level ab initio methods using both (i) one-electron spin-orbit Hamiltonian with parametrized (effective) nuclear charges in conjunction with a state-averaged MCSCF wave function as implemented by Robb in Gaussian 98 and (ii) complete one- and two-electron SOC with a fully ...