Time-resolved x-ray absorption fine structure (XAFS) spectroscopy with picosecond temporal resolution is a new method to observe electronic and geometric structures of short-lived reaction intermediates. It combines an intense femtosecond laser source synchronized to the x-ray pulses delivered into the microXAS beamline of the Swiss Light Source (SLS). We present key experiments on charge transfer reactions as well as spin-crossover processes in coordination chemistry compounds next to solvation dynamics studies of photogenerated atomic radicals.

In order to adequately describe rotation of photofragments and dynamics of vector correlations in liquids, we have generalized the J-diffusion model by allowing the rotational relaxation rate to be angular momentum dependent. The calculated nonequilibrium rotational correlation functions (CFs) are shown to decay much slower than their equilibrium counterparts, and orientational CFs of hot photofragments exhibit coherent behavior, which persists for several rotational periods. In practical terms, the standard and generalized J-diffusion models are shown to be almost indistinguishable under equilibrium conditions. Far from equilibrium, their predictions may differ dramatically.

It has been shown that among the great diversity of available vibrational modes there are two types so called h_μ- and h_α- hyston modes in the light-harvesting (LH) antennas and in the complexes of the reaction centers (RCs), which produce high modulated broadening of excitonic spectra with radically different temperature behavior. At the same time the h_μ- and h_α-modes initiate different activationless electron transfer (ET) processes in the RCs. Novel formulas is presented, which making it possible to describe known experimental data on the half-width of the B800, B850 absorption for LH2 antennas and the P870 and P960 absorption for RCs as well as on the temperature effect on the ET rate. The primary ET is considered as a resonant nonradiative transition between P* and P⁺B_A- states with next stabilization (P is a special pair, B_A is an accessory bacteriochlorophyll in A-branch of RC). It has been shown that the h_α-mode with own frequency in the range of 130-150 cm^-1 controls the primary ET from P* to bacteriopheophytin (H_A).The ET matrix elements are of 12.7 ± 0.9 and 12.0 ± 1.2 cm^-1 for Rps. viridis and Rb. sphaeroides respectively. An oscillation mechanism is discussed for ET from P* to B_A and then to H_A. It is assumed that water fulfils the transmission function in the primary ET. It is obtained that the h_μ-mode of 304 cm^-1 governs the secondary ET from H_A to ubiquinone in Rb. sphaeroides RC.

The paper presents recent experimental results on the peculiarities of fluorescence and transient absorption exhibited by indotricarbocyanine dyes in solutions of different nature. The dynamics of transient absorption spectra of the molecules under study is analyzed within the framework of the concept of intra- and intermolecular vibrational relaxation and ultrafast charge transfer in contact ion pairs.

The limitations of standard endoscopy for detection of dysplastic changes of mucosa are significant challenge and initiate development of new photodiagnostic techniques, additional to diagnostic possibilities of standard endoscopic equipment. One of the most widely examined optical modalities is the laser- or light-induced fluorescence spectroscopy (LIFS), because of its rapid and highly sensitive response to early biochemical and morphological changes in biological tissues. In the recent study delta-aminolevulinic acid/protoporphyrin IX is used as fluorescent marker for dysplasia and tumor detection in esophagus and stomach. The &dgr; -ALA is administered per os six hours before measurements at dose 20mg/kg weight. High-power light-emitting diode at 405 nm is used as an excitation source. Special opto-mechanical device is built to use the light guide of standard video-endoscopic system. Through endoscopic instrumental channel a fiber is applied to return information about fluorescence to microspectrometer. The fluorescence detected from in vivo tumor sites has very complex spectral origins. It consists of autofluorescence, fluorescence from exogenous fluorophores and re-absorption from the chromophores accumulated in the tissue investigated. Mucosa autofluorescence lies at 450-600 nm region. The fluorescence of PpIX is clearly pronounced at the 630-710 nm region. Deep minima in the tumor fluorescence signals are observed in the region 540-575 nm, related to hemoglobin re-absorption. Such high hemoglobin content is an indication of the tumors vascularization and it is clearly pronounced in all dysplastic and tumor sites investigated. After formalin conservation for in vitro samples hemoglobin absorption is strongly reduced that increases mucous fluorescence signal in green-yellow spectral region. Simultaneously the maxima at 635 nm and 720 nm are reduced.

New materials with prescribed isotopic composition could open good possibilities of functional characteristics needed for the progress in science and technology. [1]. It have been shown, that the thermal conductivity of the monocrystallic 70Ge (99,99 %) at 15 K was as much as 8.1 higher than the corresponding parameter of the natural isotopic structure [2]. Applications of the single isotopes compositions are restricted by their high cost. That's why it is very promising to find out new and less expensive methods of isotope separation and characterization of new materials [1].

Terahertz radiation affects on peptide optical properties and decreases a binding capacity of protein with native ligand. This indicates that terahertz radiation induces changes in peptide conformation.

The method of selective destruction of small chiral molecules of a specified configuration, which is based on coherent action of the intense multicomponent ps and fs laser pulses, is suggested. Computer simulation results show its efficiency for the laser distillation of a racemic mixture of randomly oriented molecules in a gas phase at room temperature.

A pyrene-flavin (isoalloxazine) dyad (PFD) and a phenothiazine-phenylene-isoalloxazine dyad (PPF), dissolved in dichloromethane are characterized by absorption and emission spectroscopy. These dyads are model compounds for flavin based blue-light photoreceptors. Absorption cross-section spectra, fluorescence quantum distributions, fluorescence quantum yields, and fluorescence decay times are determined. The absorption spectra of the dyads resemble the superposition of the absorption spectra of the constituents (1-methylpyrene, isoalloxazine, and phenylphenothiazine). Photo-excitation of the flavin moiety causes fluorescence quenching by reductive electron transfer in thermodynamic equilibrium with the exited flavin subunit. The charge-separated states recover by charge recombination. Photo-excitation of the pyrene or phenylphenothiazine moiety causes oxidative electron transfer with successive recombination, and additionally Förster-type energy transfer and Dexter-type energy transfer. For PFD in dichloromethane the rates of reductive electron transfer and oxidative electron transfer were determined to be (5 ps)^-1 and (77 ps)^-1, respectively, and a charge recombination time of about 16 ps was found. For PPF in dichloromethane the rates of reductive electron transfer and oxidative electron transfer were determined to be (700 fs)^-1 and (100 ps)^-1, respectively. The HOMO level position of the pyrene radical cation subunit relative to the HOMO level of the excited isoalloxazine subunit is determined from the delayed fluorescence emission of the PFD sample.

It is shown that stability of Henyey-Greenstein phase function gives a possibility to solve quickly a multiple-scattering light propagation problem with the same a priori information about interaction as in the primary problem definition.

As a result of an analysis of macromolecules properties in the coherent optical radiation field and with allowance for the experimentally obtained unique data on the interaction of lazer radiation with biomolecules (dependence of the interaction efficiency on the coherence length, presence of the effect in the spectra region far from the absorption band), a mechanism of wave interaction is developed. Using this mathematical model, the calculations of a change in the macromolecules oscillatory energy in the coherent radiation field are performed. It is shown that the increase of macromolecules oscillatory energy depends strongly on the coherence length of radiation. On exposure to noncoherent radiation, the biomolecules oscillatory energy practically does not change, whereas on exposure to laser radiation (coherence length ≈3 cm), energy of oscillations of atoms increases by an order of 2÷4, which results in a change in the conformation of biomolecules and activity of enzymes. Recently a lot of data are received concerning the change of lysosomal enzymes activity in blood plasma under action of laser radiation.

In this paper we report on the study of S₂→S₀ blue fluorescence and two-photon absorption (TPA) for a series of Zn-tetrabenzoporphyrins (Zn-TBP) with sequential substitution of phenyl groups in meso-positions. The blue fluorescence has been measured with both one- and two-photon excitation. The data on TPA showed that lowest g-parity state lies above B-state for all these compounds and blue fluorescence has been detected upon two-photon excitagtion at g→g transition energies above that of Soret band. The data are in line with the suggested role of the g-parity low-lying state in the nonradiative deactivation of B state. More than two-fold decrease in the relative yield of blue fluorescence was found in going from Zn-monophenyl-TBP to Zn-tetraphenyl-TBP. The enhancement of the radiationless internal S₂→S₁ and S₁→S₀ conversion and the decrease in the quantum yield of blue fluorescence was proposed to explain by nonplanar distortions of tetrapyrrolic macrocycle in Zn-tetraphenyl-TBP. The obtained results indicate that the positioning of g-parity excited states above B states is a requirement but not the sufficient condition for presence of blue fluorescence.

Field enhancement coefficient was calculated for silver and palladium clusters photodeposited on titan dioxide nanoparticle. It was shown that experimental fluorescence enhancement can qualitatively be explained by plasmon resonance and nanosystem geometry.

It has been demonstrated that chlorin e₆ form molecular complex with polyvinylpyrrolidone. The binding constant and the number of binding sites have been determined as Κ= (2.5 ± 0.5)•10⁴ M^-1 and N = 2.1 ± 0.5, respectively. Complex in comparison with free chlorin e₆ possesses increased fluorescence quantum yield, triplet and singlet state lifetimes, slightly modified intersystem crossing quantum yield, and also more intensive and red shifted absorption band locating in the "phototherapeutic window" of biological tissues. The photophysical properties of chlorin e₆ incorporated into the polymer are insensitive to pH. The formation of the complex leads to the disruption of chlorin e₆ aggregates at acidic pH. Binding to polymer only slightly improves photophysical properties of photosensitizer and should not provoke fundamental changes in PDT efficiency.

Rapid prototyping (RP) and manufacturing (M) is a novel layer-by-layer fabrication technique which has become increasingly popular due to its inherent flexibility for the manufacture of simple and complex 3D parts. Early we had been shown opportunity of selective laser sintering (SLS) of different type powder systems (intermetallics, ceramics, ferrites, high-temperature superconductors), traditional use for self-propagated high-temperature synthesis (SHS). The non-thermal heating affect of an external electromagnetic field during SHS is related to the specific system under study due to differences in movement of defects and ions at the 'plasma-like' molten combustion wave front. We have developed and refined the testing scheme for electro-thermal phenomena studies which can directly influence on the SHS combustion wave front. This work studies electromotive force (EMF) measurements across the front of combustion wave during layer by layer surface laser sintering of exothermal powder compositions (Ni-Ti, Ni-Al). Analysis using an analog-digital-analog computer converter allowed some control of the laser movement and hence some control of the exothermal reaction - in so doing it provided near optimum conditions for forming layered 3D articles. Comparative results of structural-phase transformation during laser control SHS in reaction-capable compositions are presented.

Modeling of kinetics of photoprocesses in polyatomic molecules based on four-level energy scheme is carried out. The model includes the processes in dye under cw photoexcitation and takes into account a reverse intersystem crossing and photochemical reaction from the upper triplet states. The analytical time-dependent relation for dye concentration of the initial form was obtained taking into account the contrast of rates of various photoprocesses and using of quasistationary approximation. It was shown that rate constant of photolysis correlates with probability of intersystem crossing of the dyes. For the xanthene dyes in gelatin it was shown that simple experimental method of cw laser photolysis combined with the kinetic model could be effective technique of study of upper excited states participation.

In this paper we report the spectral manifestation of existence two spectral forms of Pd-porphin in wide set of Shpol'skii matrices at cryogenic temperatures. The short-wavelength spectral form is attributed to the structure, where the central Pd(II) ion is in plane of the porphyrin macrocycle, while the long-wavelength form is associated with the nonplanar saddle-type conformation of the PdP. The frequencies of the normal vibrations in the ground electronic state have been measured separately for both forms and the differences in the normal modes of two macrocycle conformations are discussed. The type of molecule distortion has been established with using information about the frequencies of vibronic modes from high-resolved spectra of metalloporphins. Matrix effect was shown to have significant role in the stabilization of each of two conformations.

In this paper we report the spectral manifestation of different spectral forms obtained for Mg-, Zn-, Pd- and Pt-porphins in solid matrices (Shpol'skii matrices, solid tetrahydrofuran and rare gas matrices) at cryogenic temperatures. The planar and two kinds of distorted conformations of Mg-, Zn-porphins in highly-resolved fluorescence spectra have been detected. For Zn-porphin distorted forms have been detected in the fluorescence and phosphorescence spectra simultaneously. In the phosphorescence spectra of the Pd- and Pt-porphins the manifestation of the two forms in the ground state has been proved also. Energy splitting in the phosphorescence spectrum of the Pd-porphin in n-octane at 4,2 K comes to 78 cm^-1 for two forms of the Pd-porphin. Under selective excitation in S₀-S₁ channel the large set of sharp lines was detected for each of two forms and vibrational frequencies have been determined. In highly-resolved phosphorescence spectra of Pt-porphin in n-octane at 4,2 K we have detected similar manifestation of the two spectral forms in the phosphorescence spectrum. To estimate the type of molecule distortion the information about the frequencies of vibronic modes from well-resolved spectra of metalloporphins have been used.

In 1990 the activation process model was proposed [1]. Development of the activation process model [2,3] led to description of either adiabatic or non-adiabatic processes for a molecular structure transformation [4]. The model is based on two simple assumptions: 1. During the transformation process, the potential energy of a molecular particle changes discretely or in quanta: the transformation process appears to be a series of quantum subsystems occurring in sequence (these subsystems may also be defined as identical quantum oscillators); 2. In the field of IR-laser radiation, an energy exchange between IR radiation and atoms of the molecular particle results in discrete translation of these atoms which absorb oscillation energy by identical quanta up to molecular structure complete transformation. The numerical simulation carried out according to the model offered has allowed to describe such processes as: dissociation of SF6 molecule [4] and styrene ion C₈H₈ ⁺ [5]; selfdiffusion processes in Si, Ge and GaAs clusters [6]; folding and insertion for the &bgr;-barrel outer membrane protein A (OmpA) of Escherichia coli into dioleoylphosphatidylcholine (DOPC) bilayers [7]. So, we can see this model has a significant field of application to the activation processes stimulated by IR laser radiation.

Laser-magnetic field action on blood in vivo was studied within a range 440-650 nm. The primary mechanisms of laser-magnetic blood irradiation in vivo were studied at (1) laser and non-laser irradiation with light of various wavelengths, (2) autohemo-magnetic-therapy, (3) multicolored over-vein irradiation of the blood, (4) the laser-magnetic field actions. Hemoglobin is considered as primary photoacceptor of radiation. The dependence of effectiveness of laser action on light wavelength was compared with known action spectra for blood photostimulation. Magnetic field enhancement of the laser- induced reactions was discussed as result of magnetic field influence on ferromagnetic hem inclusions and on a structure of hemoglobin peptide chains. Hemoglobin oxygenation or deoxygenation processes were analyzed as a first stage of the therapeutic effects depending on a preceding hemoglobin oxygenation degree at pathological state. The laser- magnetic irradiation causes tendency to the normalization of these process. It is proposed that the secondary reactions are initiated by reversible structural changes of erythrocytes membrane caused the strong hemoglobin absorption.

The dynamics and pathways of relaxation processes in meso-ortho-nitrophenyl substituted octaethylporphyrins OEP-OEPPh(o-NO₂) and PdOEP-Ph(o-NO₂) occurring with the participation of the S₁ and T₁ states was studied in polar Ph((dimethylformamide) and nonpolar (toluene) solvents at 295 and 77 K using pico- and nanosecond laser kinetic spectroscopy. At 295 K, steric interactions between bulky β-alkyl substituents and ortho-nitro groups of meso-phenyl in these compounds create optimal conditions for overlapping of molecular orbitals of the porphyrin macrocycle (donor) and NO₂-group (acceptor), thus leading to an efficient photoinduced electron transfer (PET). For free-base OEP-Ph(o-NO₂), PET occurs only via the porphyrin S₁ state within 40 ps (dimethylformamide) and 125 ps (toluene), whereas the competing intersystem crossing S₁ ~~>T₁ is low probable. For metallocomplex PdOEP-Ph(o-NO₂), PET involves both S₁ and T₁ states. In the last case, the direct PET from the T₁ state to CT state also occurs within picosecond range (20 and 46 ps for dimethylformamide and toluene, respectively, at 295 K). Rate constants for PET with participation of T1 states are by 3-5 times smaller with respect to those found for PET occurring via the S₁ state. For both compounds, the observed long-lived component (250-700 ns) in decays of the transient T₁-T_n absorption is due to the recombination processes of radical-ion pairs whose lifetime decreases with an increase of the surrounding polarity and is hardly dependent on the presence of molecular oxygen in the solution. For both compounds, PET is completely absent in rigid solutions at 77 K.