Luminescence and Electrical Properties of CdS Films Doped with Potassium and Sodium

CdS films, both pure and doped with the alkali metals Na and K, with Cl and without it, obtained by the aerosol pyrolysis method from thiourea coordination compounds at a temperature of 250 to 500°C are investigated. The photoluminescence spectra and the dependence of the luminescence intensity on the duration of exposure of samples to a high-power UV radiation have been obtained. The doping of samples results in a tenfold increase in the intensity of the luminescence band in the visible spectrum range (650–850 nm) as compared to pure samples of CdS. Upon irradiation of samples by high-power UV radiation for 1 h, no noticeable change in the intensity of luminescence of CdS films was observed. This is indicative of the stability of the films under study against the action of UV radiation. The luminescent properties of the films, obtained pyrolytically using thiourea coordination complexes, are determined by the synthesis conditions as well as by the chemical nature of the original substances. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 509–513, July–August, 2005.     

The effect of electron irradiation on the optical properties of the natural armenian zeolite-clinoptilolite

Infrared (IR) absorption and luminescence in chemically and radiation-modified natural Armenian Zeolite (clinoptilolite) samples have been studied. The luminescence was studied in 390–450 nm and 620–710 nm wavelength bands, and the IR measurements were carried out in the 400–5400 cm⁻¹ range. It is shown that the luminescence intensity depends on the content of pure clinoptilolite in the samples and, probably on the distribution of “passive” luminescence centers over Si and Al sites that became “active” under radiation or chemical treatment. The samples of electron irradiated clinoptilolite have higher luminescence intensity than the chemically and thermally treated ones. A decrease in the intensity of IR absorption bands at 3550 cm⁻¹ and 3650 cm⁻¹ was found after irradiation.     

Photosensitivity and thermosensitivity of polymers doped with Eu(fod)<Subscript>3</Subscript> molecules

We have studied the photoluminescence (PL) spectra of Eu³⁺ ions and the decay kinetics for the photoluminescence intensity on exposure to temperature and UV radiation in polypropylene and oligo(urethane methacrylate) (OUM) doped with Eu(fod)₃ molecules (fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octadione) by soaking in a supercritical CO₂ solution. We have established that the decay kinetics for the photoluminescence intensity on exposure to UV radiation depends on the temperature of the sample and the concentration of the dopant in it. Based on studies of the spectral characteristics of doped OUM samples, we suggest that this material can be used as a two-color luminescent temperature sensor. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 104-111, January-February, 2009.     

Absorption by CS<Subscript>2</Subscript> molecules on “hot” band emission lines from a TEA CO<Subscript>2</Subscript> laser

We have measured absorption of emission from a TEA CO₂ laser, lasing on hot band lines, in pure CS₂ and a mixture of CS₂ with air, and we have determined the optimal lines for optical excitation. Numerical modeling has shown that as the peak intensity of the pump radiation is increased, we observe absorption saturation, the extent of which decreases as the pressure increases. The major factor responsible for absorption saturation is the “rotational bottleneck” effect. Depending on the peak intensity of the radiation, addition of a buffer gas can lead to an increase or decrease in the absorption. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 61–66, January–February, 2007.     

A continuously-tunable picosecond laser radiation source in the UV spectral region

We present the results of research on continuous tuning of a neodymium laser radiation frequency in the UV and vacuum ranges. We obtained generation of the total frequency of the waves of the second harmonic and of parametric light generator radiation in the UV region (338–366 nm). We investigate the optimum conditions for tuning UV radiation in the 113.5–117.0 nm range in the process of generation of the third harmonic in xenon and its mixtures with other gases. In the vacuum UV range investigated, an efficiency of generation of the third harmonic of ∼5·10⁻⁴ and a tuning range above 2600 cm⁻¹ are realized. Scientific Industrial Association “Akadempribor”, Academy of Sciences of Uzbekistan, Akademgorodok, Tashkent, 700143, Uzbekistan. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 528–535, July–August, 1997.     

Possible use of provitamin D<Subscript>3</Subscript> photoisomerization for spectral dosimetry of bioactive antirachitic UV radiation

The possible use of a simplified UV absorption spectroscopic method for dosimetry of bioactive antirachitic UV radiation has been analyzed. The method is based on the observation of the phototransformation kinetics of the provitamin D₃ primary molecule in ethanol (in vitro vitamin D₃ synthesis model) by measuring the decrease in the optical density at a fixed wavelength during UV exposure. The method can be used successfully for artificial UV sources with a constant radiation spectrum. However, such a technique turns out to be inapplicable to solar UV dosimetry in view of the variability of the solar UV spectrum that results in a varying rate of formation of irreversible photoproducts. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 256–260, March–April, 2009.     

On the effect of ultraviolet radiation on water vapor absorption of submillimeter waves

The submillimeter absorption spectra of pure water vapor and a water vapor + dry air mixture are experimentally studied under the conditions of illumination of the gas sample by ultraviolet (UV) radiation. The measurements were carried out by a vacuum echelette spectrometer in the wave number range 21.5–56 cm⁻¹ with spectral resolution 0.4–0.9 cm⁻¹, using a DRT-375 mercury-vapor discharge lamp as the source of UV radiation. In contrast to the results of similar experiments performed by other researchers, the data presented here demonstrate the absence of a noticeable effect of the UV radiation on the absorption spectra of the gas samples used. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 5, pp. 581–587, May, 1998.     

Spectral signs of photochemical reactions when blood is exposed <Emphasis Type="Italic">in vivo</Emphasis> to therapeutic doses of ultraviolet radiation

We have used the absorption spectra of whole blood, erythrocytes, and plasma to study photochemical reactions initiated by exposure of blood in vivo to UV radiation (UV irradiation) in the UV-visible and IR regions of the spectrum. We have established that when blood is exposed to therapeutic doses of UV radiation (0.5 J/cm²), the absorption of blood proteins decreases as monitored using the UV absorption and luminescence bands of the proteins; photochemical reactions are initiated in the protein and heme components of the hemoglobin. For the studied doses, the reversible reaction of photodissociation of hemoglobin complexes with oxygen is one of the most likely primary reactions initiated by UV irradiation of blood. We conclude that changes in the position and relative intensities of the IR absorption bands of the peptide groups (stretching and bending vibrations of NH, CN, and CO bonds) may be due to conformational transitions in the blood protein macromolecules, induced with a change in the intermolecular hydrogen bonds on absorption of the UV radiation by the blood. The changes in the absorption spectra of blood initiated by UV irradiation are compared with the results of laboratory blood analyses. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 400–405, May–June, 2008.     

Emission properties of thin films of electroactive doped polymers

We have studied the effect of the intensity of the exciting radiation and the temperature on the emission properties of two kinds of thin-film samples based on blends of two types of organic electroactive materials: polyfluorene + iridium triphenylpyridinate and polyepoxypropylcarbazole + zero-th order PAMAM dendrimer with eosin. We have shown that an increase in the excitation intensity leads to an increase in the intensity of the luminescence of the polymer matrices and the iridium complex up to a power density of 300 kW/cm², and the emission of the dendrimer is rapidly saturated and does not return to the initial value when the excitation level decreases. Heating up to 170°C followed by cooling causes an increase in the intensity for all the components except the dendrimer. The data obtained show that annealing is an important method for improving the emission efficiency of the proposed thin-film structures, due to a change in the packing of the activator molecules in the polymer matrix leading to more efficient transfer of the excitation energy. Molecules of the studied dendrimer are not stable when exposed to optical radiation and temperature. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 820–825, November–December, 2007.     

Luminescent analysis of photoinduced detoxification of phenol in the presence of humic substances

We have studied the effect of two detoxifying factors on aqueous solutions of phenol: UV radiation from different sources, and humic substances. The phenol photoconversion processes were monitored by the fluorescent method; the toxicity of the phenol solutions was monitored using a bioluminescence test. It was shown that effective detoxification of an aqueous phenol solution occurs as a result of addition of humic substances; the most effective photoinduced detoxification was detected when using UV radiation from an exciplex lamp (λ_rad = 308 nm). Other UV irradiation sources and the combined action of UV irradiation and humic substances are characterized by a smaller detoxifying effect. In this case, irradiation using an exciplex lamp (λ_rad = 222 nm) increases the toxicity of the phenol solution both in the presence and in the absence of humic substances. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 741–745, November–December, 2006.     

Enhanced photosensitivity in sol–gel derived 20GeO2:80SiO2 thin films

We investigate the photosensitivity of binary 20GeO₂:80SiO₂ (germanosilicate) inorganic films. The samples have been fabricated by the sol–gel spin-coating method and the densification has been performed by rapid thermal annealing at various temperatures ranging from 500 °C to 1000 °C. The –OH absorption bands in the Fourier-transform infrared (FTIR) spectra and the refractive-index data show that the films annealed below 900 °C are porous and the films annealed at 900 °C and above are dense. An ultraviolet (UV) KrF laser at 248 nm has been used to induce the change in the refractive index of the samples. We have achieved a large refractive-index change (Δn) of 0.0098 after UV illumination in excess of 1 min for our dense germanosilicate films. This UV-induced refractive-index change is attributed to the formation of GeE’/SiE’ centers from Ge–Ge/Si–Si (neutral oxygen monovacancy) and Ge²⁺ centers and to the creation of oxygen deficiency related defects. From our experiments, the oxygen deficiency related defects correspond to the absorption band at 620–740 cm^-1 in the FTIR spectra and these are the defects which make a large contribution to Δn. The attenuation coefficient of the as-deposited and UV-illuminated dense samples is about 0.42 dB/cm at 1550 nm. For porous samples, UV exposure has densified the samples to some extent. PACS 82.50.Hp; 71.23.Cq; 81.20.Fw     

Fluorescent analysis of photoinduced biodegradation of cresol isomers

We have used fluorescence spectroscopy to study photoinduced biodegradation of ortho-cresol, para-cresol and mixture of them in water when excited by different UV radiation sources. We show that the efficiency of photolysis for both the individual isomers and the mixture of cresols is higher for excitation by radiation at λ ∼ 222 nm. Pre-irradiation of aqueous cresol solutions slows down subsequent biodegradation. Using a combination of UV irradiation and the strain Penicillium tardum H-2 for utilization of the cresol mixture led to complete degradation of para-cresol and partial degradation of ortho-cresol. Spectral and chromatographic study of the qualitative composition of the metabolites formed during biodegradation of para-cresol showed that preparatory metabolism of such compounds occurs both through oxidation of the methyl group with formation of 4-hydroxybenzoic acid and through hydroxylation with formation of 4-methylcatechol. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 250–255, March–April, 2008.     

Effect of alkali-metal doping on photoluminescence of CdS films

It is established that doping of CdS polycrystalline films with alkaline metals (Li, Na, K, Cs) results in an increase of luminescence intensity by 3–5 times compared with pure films. This increase is accounted for by the placement of alkaline-metal ions in V _Cd ²⁻ cation vacancies, which are nonradiative recombination centers in these films. From the dependences of the luminsecence intensity of the doped films on the synthesis conditions (deposition temperature, concentration of doping impurities, type of doping metal), the parameters that ensure the maximum luminescence intensity of the films are determined as T_dep ≈ 450°C and C_Me = 1·10⁻⁵ at %. The luminescence intensity decreases by 1–3% upon exposure of the films to UV light (λ_max = 365 nm, I = 10²¹ quanta·sec·cm⁻¹) for several hours. This is indicative of the stability of these films against UV radiation. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 362–366, May–June, 2007.     

Taking into account scattering of polarized laser radiation by cuvet walls when probing blood

We have studied the ratio of the intensities of radiation scattered by a layer of blood in a cuvet and by the cuvet walls for normal incidence or incidence at the Brewster angle for probing radiation from a He-Ne laser, linearly polarized in the plane of incidence (plane of observation) or orthogonal to that plane. We have compared it with the intensity of the radiation reflected by the surface of the cuvet wall, as estimated based on the geometric approximation. We have found the optimal conditions for probing and observing scattering for the layer in a cuvet, where such conditions are characterized by a minimal effect from the cuvet walls and the maximum ratio of useful signal to background. Report given at the Fifth International Scientific and Technical Conference on Quantum Electronics, 22–25 November 2004, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 270–272, March–April, 2006.     

Change in laser-induced fluorescence spectra of sea water during degradation of dissolved organic matter

We present the results of measurement of the laser-induced fluorescence spectra of sea water under laboratory conditions. We show that during phytoplankton cell death caused by heating of sea water samples, the fluorescence intensity of dissolved organic matter (DOM) increases. We observe different behaviors of the fluorescence intensity for excitation by 2nd harmonic (532 nm) and 3rd harmonic (355 nm) emission from a Nd:YAG laser during degradation of dissolved organic matter. In the first case, a monotonic decrease in the DOM₅₃₂ fluorescence intensity occurs, while in the second case the fluorescence intensity remains constant. We give a possible explanation for such behavior of the DOM fluorescence intensity. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 103–107, January–February, 2007.     

Development of a segmented fast neutron spectrometer

We discuss the development of a spectrometer based on full energy absorption using liquid scintillator doped with enriched ⁶Li. Of specific interest, the spectrometer is expected to have good pulse height resolution, estimated to lie in the range 10–15% for 14-MeV neutrons. It should be sensitive to flux rates from 10⁻⁶ cm⁻² s⁻¹ to 10⁶ cm⁻² s⁻¹ above a threshold of 500 keV in an uncorrelated γ background of up to 10⁴ s⁻¹. We have constructed a pilot version of the detector using undoped liquid scintillator, and we report its present status. The detector’s efficiency is determined by the volume of the scintillator (∼1.21) and is estimated to be 0.2–0.5% for 3-MeV neutrons. The good pulse height resolution is achieved by compensation of the nonlinear light yield of the scintillator due to the use of optically separated segments, which collect scintillations from each recoil proton separately. We demonstrate here the response of the detector to neutrons from a Pu-α-Be source, whose energies range up to 10 MeV. Initial testing indicates a low threshold (≈600 keV) and good spectral response after requiring a multiplicity of three segments. Such a spectrometer has applications for low-background experiments in fundamental physics research, characterizations of neutron flux in space, and the health physics community. The text was submitted by the authors in English.     

Indole photodissociation in the gas phase

Kinetic characteristics of the growth in delayed luminescence intensity of indole in the gas phase have been measured with excitation of the molecules in the spectral region 250–287 nm. The luminescence build-up kinetics show two components with characteristic lifetimes of about 1 and 10 μs that are associated with the formation of free radicals due to N–H bond dissociation. Two basic mechanisms for photodissociation of indole in the gas phase have been identified based on an analysis of the dependence of the kinetic characteristics for these components on the excitation radiation wavelength/intensity and the vapor pressures of indole and foreign gases. The fast component results from the dissociation of an N–H bond of vibrationally excited molecules in the ground state that is populated through internal conversion. The slow component is associated with the generation of free radicals because of annihilation of two triplet indole molecules. A dependence of the quantum yield of intersystem crossing on the excitation wavelength in the spectral region 260–287 nm has been found. It is shown that the fluorescence quantum yield drop with a decrease of the excitation radiation wavelength is caused by an increase in the internal conversion quantum yield to the electronic ground state.     

Generation of coherent tunable deep UV radiation for detection and absorption studies of explosives RDX and TNT

We report a technique for the efficient generation of tunable coherent deep UV radiation and its application in studies of RDX and TNT at the ppm level on the basis of their absorption characteristics. The obtained experimental absorption data are compared with conventional spectrophotometric data. The UV radiation in the range 200–260 nm has been generated by the type-I noncollinear third harmonic of the dye laser radiation (600–700 nm) and also by sum frequency mixing (SFM) of Nd:YAG output (1064 nm) with the second harmonic of the dye laser in β-barium borate (BBO) crystal. The maximum conversion efficiency of the generated signal is estimated to be 57.5% at λ = 218.9 nm wavelength. Apart from measurements of the absorbance of RDX and TNT at different concentrations in their respective solutions, the minimum detection concentrations have also been ascertained. The estimated minimum detectable concentration of RDX is 8.47·10⁻⁹ M, whereas that for TNT is 35.7·10⁻⁹ M. The data were obtained using only ∼100 μJ/pulse of laser energy. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 516–521, July–August, 2007.     

Continuous frequency tuning of a picosecond neodymium-glass laser in the UV and VUV

The results of an investigation of continuous frequency tuning of a neodymium laser in the UV and VUV ranges are reported. Generation of the sum frequency of second harmonic radiation and the radiation from a parametric light generator in the UV region (338–366 nm) is achieved. The optimal conditions for tuning UV radiation in the range 113.5–117.0 nm in third-harmonic generation processes in xenon and its mixtures with other gases are investigated. A third-harmonic generation efficiency of ∼5×10⁻⁴ and a tuning range >2600 cm⁻¹ are obtained in the VUV range investigated. Zh. Tekh. Fiz. 68, 82–89 (May 1998)     

Ultraviolet gas-discharge lamp on iodine molecules

The emission characteristics of a pulsed-periodic UV radiation source are reported. The source excited by a pulsed-periodic capacitive discharge initiated in helium-iodine vapor, neon-iodine vapor, or krypton-iodine vapor mixtures radiates in the spectral range 200–450 nm. It is shown that most of the plasma radiation power concentrates in the integral line of the iodine atom (206.2 nm) and in the D′-A′ band of the iodine molecule with a maximum at 342 nm. The radiation intensity of the lamp is optimized in accordance with the partial pressure of the inert gases. The discharge plasma parameters that are of interest for simulating the process kinetics and the output characteristics of an UV source based on molecular iodine, atomic iodine, and xenon iodide are calculated in helium-iodine vapor and xenon-iodine vapor mixtures.