Valey F. Kamalov

Rise and decay kinetics of photosensitized singlet oxygen luminescence in water. Measurements with nanosecond time-correlated single photon counting technique

The time-correlated single photon counting technique was applied to the measurement of photosensitized singlet oxygen luminescence induced by flash laser excitation. Rise and decay kinetics of this luminescence has been measured with 10 ns resolution in aqueous solutions of tetra (p-sulfophenyl)porphyrin at various oxygen pressures. The rise kinetics are shown to be determined by the process of energy transfer to oxygen from the triplet state of the photosensitizer. The lifetime of singlet molecular oxygen in water was measured with high precision: τΔ = 3.09±0.06 μs. The rise and decay kinetics of the singlet oxygen luminescence in aqueous suspensions of porphyrin-containing yeast cells were detected.

Time-resolved emission spectra of the BIC J-aggregate at low temperature

Abstract A red-shift and broadening of the emission of the BIC J-aggregate in glass were observed at low temperatures (4.5 K). To explain the observation a transformation of the excess excitation energy in the bath with disordering of the structure of molecular aggregate is proposed. The characteristic time of this energy transformation is 315 ps at 4.5 K for an excess energy of 400 cm −1 . Another possible mechanism of exciton self-trapping by exciton-phonon interaction is discussed.

Cubic optical nonlinearity of free electrons in bulk gold

A fast (Tau(response) <90 fs) free-electron spin-f lipping frequency-degenerate nonlinearity with a signif icant value of|chi((3))(xxyy)(omega,omega,omega,-omega)chi((3))(xxyy)(omega,omega,omega,-omega)|~10(-)(8)esu has been observed in bulk gold at 1260 nm by use of a new pump-probe polarization-sensitive technique.

Femtosecond time-resolved resonance CARS theory

Abstract A femtosecond time-dependent resonance CARS theory is developed. The resonance CARS response is calculated in the temporal representation on the basis of density-matrix equations. Two experimental schemes for the study of relaxational processes in excited electronic states which use time-delayed femtosecond pulses are discussed. The simple model of wavepacket temporal evolution is used for the calculation of the CARS depolarization ratio.

Temperature dependence of superradiant emission of BIC J-aggregates

Abstract The emission lifetime of the carbocyanine BIC J-aggregate decreased with the increase of the temperature in the range 20–60 K. Several mechanisms are proposed to explain in nonradiative relaxation of the J-aggregate observed in glass.

Two-exciton emission of BIC J-aggregates

Abstract We observed a blue-shift and narrowing of emission band of carbocyanine dye (BIC) J-aggregate in solution at high excitation intensity. This is explained by formation of a two-exciton state and efficient emission from the two-exciton to one-exciton state. The lifetime of the two-exciton state of BIC J-aggregate in solution is 30 ps at room temperature.

Excited state relaxation of crown ether styryl dyes: photoisomerization

Abstract Photophysical processes are studied in a new class of dyes containing a chromophoric part and a crown ether part (crown ether styryl dyes). Photoisomerization is proposed to be the main channel of nonradiative decay of the singlet excited electronic state. The temperature dependence of fluorescence decay was measured and the lifetime of the trans-isomer in excited electronic state was found to decrease with temperature in ethanol solutions. Isomerization around the CC bond is discussed, and the activation barrier is estimated as 2.3 and 1.5 kcal/mol for the two crown ether styryl dyes studied.

Time-resolved fluorescence of crown ether styrul dyes.

Photophsical processes are studied in a new class of dyes contining a chromophoric part and a crown ether part. Fluorescence decays were oebserved to be strongly dependent on temperature in the range from 294 to 4 K. Photoinduced isomerization and electron transfer are considered as possible mechanisms to explain the results.

Intermolecular Coherence and Vibrational Dephasing of BIC J-Aggregates

BIC J-aggregates are studied by femtosecond CARS and fluorescence spectroscopy. Subpicosecond dephasing of Raman transitions of J-aggregates is observed at room temperature, which is accompanied by femtosecond beats of Raman transitions. Temperature dependence of BIC J-aggregate superradiant decay in glass is measured.

Automated optoacoustic spectrometer for the near-infrared range based on a color-center laser and its applications in the spectroscopy of molecular gas overtones

A description is given of the construction and characteristics of an optoacoustic gas absorption spectrometer based on an LiF :F2− laser operating in the rarely employed spectral range 1.10–1.22 μ. Optimization of the parameters of the color-center laser and of the optoacoustic detector made it possible to achieve a high sensitivity (10−7 cm−1) in a wide dynamic range with a spectral resolution of 0.1 cm−1 . The spectrometer was found to be suitable for the study of overtone vibrational states of molecular gases.