The spectral narrowing of a high-power flashlamp-pumped dye laser by injection of external narrow-band radiation

A method of increasing the injection-locking efficiency by external narrow-band radiation relying on a space-frequency separation in a nonlinear absorber (spectral contraster) placed into the high-power dye-laser cavity is proposed. It is shown that this method permits an increase of the energy conversion efficiency into a narrow-band line ( 10^–3 nm) up to 90% with a laser output energy of about 1 J and a pulse duration of more than 1 µs.     

Noninvasive methods of measuring oxygen saturation in venous blood

The feasibility of measuring oxygen saturation in venous blood both by artificial modulation of the volume of tissue filled with blood and by determining the respiratory rhythm from a Fourier spectrum is demonstrated. Both methods have advantages and limitations. The results obtained by the two methods correlate well with one another and with published data.     

Electronic absorption spectra or carbonium and dicarbonium ions containing heterocyclic rings with a biphenylene base

An analysis has been made of -^* -electronic excitations of carbonium and dicarbonium ions obtained by the interaction of concentrated sulfuric or fluoboric acid with alcohols or glycols containing a heterocyclic bridge structure, i.e., nuclei of dibenzofuran, dibenzothiophene, carbazole, and N-methylcarbazole; this analysis has been aimed at establishing a correlation of their structure and spectral characteristics. From an analysis of experimental data, calculated results, and indexes quantitatively characterizing the structure of the -^* -electronic excitations, it has been established that there are four electronic transitions in the visible region of the electronic absorption spectrum of the carbonium ions. The long-wave, intense band of the spectrum is due to superposition of intense (p-type) and weak (-type) transitions proceeding from corresponding excitations of the heterocyclic fragment. In the electronic spectra of the dicarbonium ions, a doublet of p-transitions is clearly manifested. It has been shown that the interaction of chromophores through the bridge structure increases by a factor of approximately 1.8 when the change is made from dibenzofuran to dibenzothiophene, carbazole, and Nmethylcarbazole; in comparison with the corresponding dihydroxycarbonium ions, the degree of interaction of the chromophores is greater by a factor of approximately 1.5.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 3, pp. 284–291, May–June, 1990.     

The biomedical effect of laser-induced photodissociation of oxyhemoglobin in vivo

It is demonstrated that the photodissociation of oxyhemoglobin in cutaneous blood vessels and capillaries allows additional extraction of molecular oxygen, prevents hypoxia, and stimulates aerobic metabolism of cells. On the basis of the studied phenomena, a new optical technology of local oxygenation of tissue directly in the zone of laser irradiation has been developed. It is shown that the efficiency of the proposed method for laser-induced oxygenation of biotissues is comparable with the efficiency of hyperbaric oxygenation, with local action being an additional advantage. Various aspects of the applications of the new technology in modern medicine in which the elimination of local hypoxia is needed are discussed. The proposed optical method for local oxygenation of biotissues makes it possible to solve the hypoxia problem in malignant tissue and substantially increase the efficiency of photodynamic, radiation, and chemical therapy in modern oncology.     

Assessment of the therapeutic action of low-intensity laser radiation from the extent of local tissue saturation with oxygen

We propose a method for dosimetry of the biological response to laser irradiation based on determination of the amount of oxygen additionally supplied to the tissue. We show that it is feasible to determine the therapeutic dose from the change in the degree of oxygen saturation of the blood, heart rate, hemoglobin concentration in the blood, and exposure time. __________ 13Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 516–520, July–August, 2006.     

Fluorescence excitation spectra of jet-cooled amino-phthalimides

We report the fluorescence excitation spectra of the ππ¹ transition of jet-cooled 3-amino-, 3-amino-N-methyl-, and 4-amino-N-methyl-phthalimide. The spectra are dominated by a long progression of a vibrational mode v' ≈ 210 cm^-1 in combination with a few vibrational fundamentals of the excited state. The long electronic lifetimes and structural diversity of these compounds make them ideally suited for the study of intramolecular vibronic relaxation.     

New laser dyes based on 3-imidazopyridylcoumarin derivatives

A comparative analysis of the spectral-luminescent characteristics and generation parameters of a number of 3-imidazopyridylcoumarin derivatives has been carried out under nano- and microsecond excitation by coherent and incoherent light. New coumarin dyes are offered that feature the ability to lase under different types of pumping in the spectral range 525–580 nm; high lasing efficiency reaching 20% and 1% under laser and lamp pumping, respectively; and high photochemical stability (3–5 times higher than that of rhodamine 6 G) under conditions of powerful nonmonochromatic pumping.     

Minimum opaque manifolds

For various manifolds, we consider the problem of finding the set of minimum measure which intersects every geodesic.