We propose a study of dynamics of edge-emitting semiconductor laser subjected to external optical feedback. The
external cavity contains a mirror and a second semiconductor device, which can work as an amplifier or an absorber. The
existence of regimes of regular or chaotic pulsations are discussed.
Conformational transformation of dissolved humic substances induced by acidic and basic additives in water has been investigated by automated subnanosecond laser spectrofluorimeter and fluorescent probe method. The equilibrium constants for binding of rhodamine 6G to dissolved humic substances in water have been determined by a fluorescence quenching method. It is shown that the conformational structure of humic compounds in water depends on the intra- and intermolecular interactions. Spectral and viscosimetrical data in pH region 1.5-12.0 are interpreted in terms of conformational transformation of dissolved humic substances from a rigid globule to a flexible chain.
The modified electro-optical absorption and emission methods are described as well as their use for measurements of electrical dipole moments of five aminophthalimides in ground and excited states. It is found that there exists a principal difference between properties of 3- aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent on the solvent polarity, in comparison with 4ANMP. The possible mechanism of this effect is discussed.
Here we wish to present automated laser spectrofluorimeter and some applications of it. The excitation part of the spectrofluorimeter includes an atmospheric pressure nitrogen laser (pulse duration 0.35 ns, peak power 350 kW) and distributed-feedback dye laser (tuning range 400 - 750 nm, spectral width 0.1 - 0.6 nm). It is possible to excite the probe by nitrogen laser or dye laser. The signal of fluorescence is registered by boxcarintegrator and data are input into the computer IBM PC/AT-286. Laser spectrofluorimeter is full automated, lasers, all optical and electronic systems are controlled by the computer. The laser spectrofluorimeter can measure time-resolved fluorescence characteristics with temporal resolution from subnanoseconds to milliseconds: (1) instantaneous fluorescence spectra (0.2 ns - 10 ms), (2) instantaneous anisotropy spectra and anisotropy kinetics (0.2 ns - 10 ms), (3) fluorescence kinetics and lifetime of excited state (0.05 ns - 10 ms). Experimental data can be treated with a full set of programs: (1) deconvolution of fluorescence pulse with up to 3 exponential approximation, (2) calculation of anisotropy kinetics with simultaneous deconvolution for different polarization, (3) calculation of instantaneous spectra from fluorescence decays, (4) mathematical treating of spectra (position of spectrum, halfwidth, asymmetry etc.).
Using subnanosecond laser spectrofluorometry, the spectral and polarization time-resolved characteristics of 1-phenylnaphthylamine (1-AN) fluorescent probe in phospholipid bilayer and red blood cell membranes have been studied. It is shown that the electronic spectra of probe in model membranes are inhomogeneously broadened. In contrast to low-molecular weight solvents there are two reasons for inhomogeneous broadening. The first is connected with different levels of location of probe molecules in the membrane. Inhomogeneous broadening due to the first factor has a static character. The second reason is similar to that of solutions and linked with fluctuations of solvate structure. This type of broadening has a dynamic character. The process of intermolecular relaxation in membranes is accompanied by the release of the free energy excess, which results in wavelength-dependent rotation of probe.
The modified electro-optical absorption and emission methods are described as well as their use for measurements of electrical dipole moments of five aminophthalimides (APs) in ground and excited states. It is found that there exists a principal difference between properties of 3- aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent on the solvent polarity, in comparison with 4ANMP.
Conformational transformation of dissolved humic substances induced by NaOH and HCl addition in water has been investigated by automated subnanosecond laser spectrofluorimeter and fluorescence probe method. The equilibrium constants for binding of Rhodamine 6G to dissolved humic substances in water have been determined by a fluorescence quenching method. It is shown that the conformational structure of humic compounds in water depends on the intra- and intermolecular interactions. Spectral and viscosimetrical data in pH region 1.5 - 12.0 are interpreted in terms of conformational transformation of dissolved humic substances from a rigid globule to a flexible chain.
We present automated laser spectrofluorimeter and some applications of it. Laser spectrofluorimeter is fully automated. The lasers and all optical and electronic devices are controlled by the computer. The laser spectrofluorimeter can be used for measuring stationary fluorescence and anisotropy spectra, time-resolved fluorescence characteristics with temporal resolution from subnanoseconds to milliseconds: (1) instantaneous florescence spectra (0.1 ns - 10 ms); (2) fluorescence kinetics and lifetime of the excited state (0.05ense - e10ems, after mathematical treatment); and (3) anisotropy spectra and anisotropy kinetics (0.1 ns - 10 ms). Experimental data can be treated with a full set of programs: (1) deconvolution of fluorescence pulse with up to 3-exponent approximation; (2) calculation of anisotropy kinetics with simultaneous deconvolution for different polarization; (3) calculation of instantaneous spectra from fluorescence decays; and (4) mathematical treatment of spectra (position of spectrum, halfwidth, asymmetry, etc). Laser spectrofluorimeter was tested on a number of objects (dye solutions, fluorescent probe in phospholipid bilayer and red blood cell membranes, humus substances in natural water, etc.) and demonstrated its high versatility.
Using subnanosecond laser spectrofluorometry the spectral and polarization time-resolved characteristics of 1-phenylnaphthylamine (1-AN) fluorescent probe in phospholipid bilayer and red blood cell (RBC) membranes have been studied. It is shown that the electronic spectra of probe in model membranes inhomogeneously broadened. Inhomogeneous broadening affect significantly the spectroscopic properties of probe in membranes, such as the time-dependent fluorescence Stokes shift, the dependence of the fluorescence instantaneous spectra and fluorescence kinetics on excitation wavelength. The obtained results prove the existence of the earlier unknown effect of the wavelength- dependent rotation of a probe in phospholipid bilayer and RBC membranes.
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