A compact approximate groundstate of the Kondo problem is introduced. It consists of four Slater states. The spin up and down states of the localized d-impurity are paired with two localized selectron states of opposite spin. All the remaining s-electron states are rearranged forming two new optimal orthonormal bases. Through a rotation in Hilbert space the two localized states (and the rest of...

The O((3)P) + C(2)H(4) reaction, of importance in combustion and atmospheric chemistry, stands out as a paradigm reaction involving triplet- and singlet-state potential energy surfaces (PESs) interconnected by intersystem crossing (ISC). This reaction poses challenges for theory and experiments owing to the ruggedness and high dimensionality of these potentials, as well as the long lifetimes of...

The method of transient XUV photoemission spectroscopy is developed to investigate the ultrafast dynamics of heterogeneous electron transfer at the interface between the N719 ruthenium dye complex and TiO2 nanoparticles. XUV light from highorder harmonic generation is used to probe the electron density distribution among the ground and excited states at the interface after its exposure to a pum...

The electronic structure relevant to low spin (LS)↔high spin (HS) transitions in Fe(II) coordination compounds with a FeN6 core are studied. The selected [Fe(tz)6]2+ (1) (tz = 1H-tetrazole), [Fe(bipy)3]2+ (2) (bipy = 2,2'-bipyridine), and [Fe(terpy)2]2+ (3) (terpy = 2,2':6',2″-terpyridine) complexes have been actively studied experimentally, and with their respective mono-, bi-, and tridentate ...

Single-molecule Förster resonance energy transfer (FRET) experiments are an important method for probing biomolecular structure and dynamics. The results from such experiments appear to be surprisingly independent of the excitation power used, in contradiction to the simple photophysical mechanism usually invoked for FRET. Here we show that excited-state annihilation processes are an essential ...

Understanding the mechanism of singlet exciton fission, in which a singlet exciton separates into a pair of triplet excitons, is crucial to the development of new chromophores for efficient fission-sensitized solar cells. The challenge of controlling molecular packing and energy levels in the solid state precludes clear determination of the singlet fission pathway. Here, we circumvent this diff...

We present a theoretical approach to investigate the electron spin polarization (ESP) of the excited triplet state that has been detected by using the time-resolved EPR (TREPR) method in the Photosystem II reaction center (PS II RC) of the plants. We show, by using the stochastic-Liouville equation, that the ESP pattern created in the accessory chlorophyll (ChlaccD1) which reside near the PD1 c...

Photon-induced electronic excitations are ubiquitously observed in organic chromophore. In this context, we present a simple, alternative time-independent DFT procedure, for the computation of single-particle excitation energies, particular, lower bound excited singlet states, which primary interest photochemistry. This takes inspiration from recently developed Becke’s exciton model, where key ...

Transient and steady state optical spectroscopies were used to study thin films made from a series of polyfluorene polymers blended with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in order to determine the influence of polymer ionisation potential on photoinduced charge separation. We find that the energy of the charge separated state DeltaE(CS), given by the energy difference between th...

The manuscript focuses on the properties of phthalocyanines (Pcs) that are required for them to be employed as photosensitizers in applications such as photodynamic therapy (PDT). High triplet-state quantum yields and lifetimes as well as high singlet-oxygen quantum yields are required for a good photosensitizer. In addition, absorption of the photosensitizer in the red region of the electromag...