Radiation Of Different Wavelengths Research Articles

Enhanced harmonic generation in C60-containing plasma plumes

The results of enhanced harmonic generation in fullerene-containing plasma plumes using laser radiation of different wavelengths, pulse durations, and phase modulation are presented. Odd and even harmonics up to the 29th order of 800 nm radiation have been extended in the case of two-color orthogonal polarization pump of C60-containing plasma plumes. The conversion efficiency for the odd and even harmonics in the vicinity of SPR of the C60-containing plasma (40–70 nm) was estimated to be in the range of 10−4.

The Luminescence of Nanoscale Y2Si2O7:Eu3+ Materials

The Y2Si2O7:Eu3+ sample was prepared with the sol-gel method. The Y2O3:EU3 was dispersed in SiO2, and the complex Y2Si2O7:Eu3+ particles were synthesized at high annealing temperature. The sample consisted of nearly spherical particles with an average size about 60 nm. The ultraviolet excitation spectra and emission spectra were measured. The sample excited by short ultraviolet light showed strongly red luminescence and fine monochromaticity. The luminescence was strongest from the 5D0 --> 7F2 electric dipole transition located at 611 nm. The excitation spectra of Y2Si2O7:Eu3+ excited with ultraviolet lights showed that the peak of the Eu(3+)-O2- charge transition band located at about 240 nm. During monitoring of different emission peaks of 5D0 --> 7F2, the charge transition band in the excitation spectra shifted, and the relative intensity of emission spectra changed obviously under the excitation of different ultraviolet wavelengths. These results confirmed that the Eu3+ could be excited with ultraviolet radiation of different wavelengths. At low temperature, using Eu3+ ions as fluorescence probes, we monitored the emission peaks of 5D0 --> 7F1 and 5D0 --> 7F2 transitions and measured the excitation spectra of 7F0 --> 5D0, 5D0 --> 7F1, and 5D0 --> 7F2 site-selective excitation spectra. These results indicated that Eu3+ ions are located in different local environments in the Y2Si2O7 host.

Structure and properties of copper coatings electrodeposited under X-ray radiation

142-145The influence of X-ray radiation of different wave lengths on the structure and properties of electrodeposited copper coatings is found. It is determined by the methods of X-ray structure analysis and optical and scanning microscopy that, in the process of electrodeposition, X-ray radiation changes the primary structure of electrolyte and leads to a decrease in the grain size of deposits and an increase in the microhardness and degree of dispersion of mosaic blocks. The radiation effect on the process of electrodeposition is accompanied by an increase in the rate of material deposition on the cathode due to intensification of the diffusion of electrolyte components to the cathode.

Influence of C60 morphology on high-order harmonic generation enhancement in fullerene-containing plasma

The morphologies of the fullerene targets and the ablated fullerenes to determine the optimal conditions of excitation of the C60-containing targets have been analyzed. The optimization of fullerene-containing plasma conditions allowed the enhanced harmonic generation in these plasmas using laser radiation of different wavelengths, pulse durations, and phase modulation. A comparison between the harmonic generation in single-atom/ion-containing plasmas (using bulk carbon, silver, and indium targets) and fullerene-rich plasma plumes showed better conversion efficiency for the latter medium. The influence of phase modulation of the fundamental radiation in fullerene plasmas on the spectral properties of harmonics has been studied.

Development of a silver ion source using nanosecond pulses of a Nd:YAG laser at different wavelengths

A silver ion source was designed by focusing the fundamental and harmonics of Q-switched Nd:YAG laser pulses onto a silver target and simultaneously applying an electric potential in an argon environment. The silver ions were detected at a distance of 2 cm from the target surface using a Faraday cup ion probe after letting them pass through a retarding mesh grid (copper electrode). We aim to produce and characterize the silver ions generated by the laser radiation of different wavelengths and pulse energy, ambient gas pressure and the electrode spacing under applied electric field. In addition to this, the effect of laser radiation on plasma under vacuum and at different argon gas pressures was investigated. The velocity distribution function of the plasma emitted from the silver target was investigated under argon discharge. These measurements demonstrated clearly that the velocity distribution function and current signals depend on laser power, laser wavelength and argon pressure. We observed a ten fold increase in the plume current with increase in the applied voltage and ion velocity in the presence of a laser field. The surface morphology of the laser irradiated samples was investigated using reflection optical microscopy.

DC corona ozone generation enhanced by TiO2 photocatalyst

Non-thermal electrical discharges, such as corona discharge are apart of the source of ozone, charged, and excited species and acoustic noise also the source of electromagnetic radiation of different wavelengths. The important component of this radiation from the standpoint of photocatalyst activation is the ultraviolet radiation. We studied the role of UV radiation on corona discharge ozone production by placing the titanium dioxide photocatalyst into the discharge region. We used hollow needle to mesh DC corona discharge at atmospheric pressure with TiO2 globules on the mesh. The discharge was enhanced by the flow of air through the needle. We found that for the needle biased negatively addition of TiO2 photocatalyst on the mesh electrode drastically increases discharge ozone production as well as the ozone production yield. These quantities are also influenced by the mass of the used photocatalyst and its distribution in the discharge chamber.

A long‐term evaluation of erythema and pigmentation induced by ultraviolet radiations of different wavelengths

The long-term reactions of human skin by different ultraviolet (UV)-wavebands were not reported. This study was to investigate a time course of erythema and pigmentation induced by UVA-1, broadband UVA (BBUVA), narrowband UVB (NBUVB) and broadband UVB (BBUVB). Ten volunteers participated in this study for 6 months. Four skin areas, from the back of each subject, were irradiated with two minimal erythema dose (MED) of four different UV wavelengths corresponding to UVA-1, BBUVA, NBUVB and BBUVB. For both UVA-1 and BBUVA, erythema and pigmentation were most pronounced immediately and 1 h after exposure. Erythema rapidly diminished but pigmentation persisted throughout the study. For both NBUVB and BBUVB, test areas reacted with erythema of maximum intensity at 1 and 2 days, respectively. A maximum tanning was reached at 3-6 days for NBUVB and 4-7 days for BBUVB, and the return toward the original point was at 1 and 3 months, respectively. Two MED of UVA produced far prolonged erythema and pigmentation than UVB. For UVA, UVA-1 and BBUVA showed similar intensity and time course of skin reaction. For UVB, erythema and pigmentation produced by NBUVB were milder in intensity and shorter in a time course than those by BBUVB.

Long‐term evaluation of erythema and pigmentation induced by ultraviolet radiations of different wavelengths

Although multiple studies have been reported about the biological effects of ultraviolet (UV) radiations, the comparative and long-term reactions of human skin by several different UV-wavebands were not reported. The aim of this study was to investigate a time course of erythema and pigmentation induced by UVA 1, broad-band UVA (BBUVA), narrow-band UVB (NBUVB) and broad-band UVB (BBUVB). Ten volunteers participated in this study for 6 months. Four skin areas, from the back of each subject, were irradiated with two minimal erythema dose (MED) of four different UV wavelengths corresponding to UVA 1, BBUVA, NBUVB and BBUVB. Skin color changes were evaluated by visual scoring and values were converted into the L*a*b color system. For both UVA 1 and BBUVA, erythema and pigmentation were most pronounced immediately and 1 h after exposure. Thereafter, erythema rapidly diminished but pigmentation persisted throughout the study. For both NBUVB and BBUVB, test areas reacted with erythema of maximum intensity at 1 and 2 days, respectively. A maximum tanning was reached at 3-6 days for NBUVB and 4-7 days for BBUVB, and the return toward the original color point was at 1 and 3 months, respectively. No significant difference was found in visual and colorimetric evaluation for the time course of skin color changes. Two MED of UVA produced far prolonged erythema and pigmentation than UVB. For UVA, UVA 1 and BBUVA showed similar intensity and time course of skin reaction. For UVB, erythema and pigmentation produced by NBUVB were milder in intensity and shorter in time course than those by BBUVB. These results would provide standard data on time courses and intensity of skin color changes by different UV wavelengths.

Photochromism, bleaching and photorefractive recording in undoped Bi12TiO20 crystals in the visible and near infrared wavelength range

Abstract We describe the effect of radiation of different wavelengths in the visible and near infrared range over photochromism, bleaching and photorefractive recording on undoped Bi12TiO20 crystals. These experiments lead to a phenomenological description of the relevant photoactive centers in this material. At least an empty donor level 0.42 eV below the conduction band, some deeper donor levels up to 1.6 eV below the conduction band and an acceptor level 1 eV above the valence band were identified.

Effect of UVA and UVB Irradiation on the Metabolic Profile of Rabbit Cornea and Lens Analysed by HR-MAS 1H NMR Spectroscopy

Purpose:The aim of the study was to investigate the metabolic profiles of intact rabbit corneas and lenses exposed to UVA and UVB radiation by using high-resolution (HR) magic angle spinning (MAS) ¹H nuclear magnetic resonance (NMR) spectroscopy and pattern recognition methods. Methods:Adult albino rabbits were exposed to UVA (366 nm, 0.589 J/cm²) or UVB (312 nm, 1.667 J/cm²) radiation for 8 min, once a day for 5 days. Three days after the last irradiation day, samples of corneas and lenses were dissected. HR-MAS ¹H NMR spectroscopy combined with pattern recognition methods (principal component analysis and soft independent modelling of class analogy) and one-way ANOVA were applied to obtain metabolic information from intact corneal and lens tissue. Results: UVB irradiation caused statistically significant metabolic changes in the rabbit corneas. A decrease in metabolites as ascorbate (84%), myo-inositol (59%), hypotaurine (91%) and choline (76%) was observed. Exposure to UVA radiation caused no significant metabolic alteration in this tissue. The metabolic profile of the rabbit lenses showed no detectable changes after UVA or UVB exposure. Conclusions:The combination of HR-MAS ¹H NMR spectroscopy and multivariate methods proved effective to analyse intact corneal and lens tissue after exposure to UV radiation of different wavelengths. By avoiding extraction methods and obtaining complete metabolic profiles from one sample, HR-MAS ¹H NMR spectroscopy provided important information about metabolic alteration occurring in rabbit corneal and lens tissue after UV exposure.

Ultraviolet Induced Thermoluminescence in Gadolinium-Doped Zirconium Oxide Films

This paper presents the results of studying the thermoluminescent (TL) characteristics of Gadolinium-doped Zirconium oxide (ZrO2:Gd) films. Samples were prepared by the spray pyrolisis method depositing them on different substrates using various concentrations of the dopant and exposing to UV radiation of different wavelengths in the range from 200 to 330 nm. Optimum concentration of the dopant determined on the base of maximum TL response was 12% when films were exposed to 260 nm UV light. At these conditions, ZrO2:Gd films presented a glow curve exhibiting two peaks at 110°C and 290°C, a broad range linear TL response as a function of spectral irradiance and a fading of the order of 11% in a week. No significant differences were observed in the TL characteristics of the films deposited on quartz or glass substrates. These results suggest that ZrO2:Gd films could be used in UV radiation measurement.

Nanotube Optoelectronic Memory Devices

Nanotube transistors are coated with optically responsive agents to form optoelectronic detectors. In response to illumination, an electronic property of the inventive detector changes from one value to another. It retains the new value when the illumination is removed, so that the detector remembers having been illuminated. The detector can be reset by changing a gate voltage. Spectral response of the detectors can be changed by using different agents as coating. Multiple detectors with different agents can be combined on one substrate to form a combined detector that discriminates between radiation of different wavelengths.

Effect of low-intensity (3.75-25 J/cm2) near-infrared (810 nm) laser radiation on red blood cell ATPase activities and membrane structure.

The biostimulation and therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the exact mechanism of action of the laser radiation with living cells is not yet understood. The aim of the present work was to investigate the effect of laser radiation (810 nm, radiant exposure 3.75-25 J/cm(2)) on the structure of protein and lipid components of red blood cell membranes and it functional properties. The role of membrane ATPases as possible targets of laser irradiation was analyzed. A variety of studies both in vivo and in vitro showed significant influence of laser irradiation on cell functional state. At the same time another group of works found no detectable effects of light exposure. Some different explanations based on the light absorption by primary endogenous chromophores (mitochondrial enzymes, cytochromes, flavins, porphyrins) have been proposed to describe biological effects of laser light. It was suggested that optimization of the structural-functional organization of the erythrocyte membrane as a result of laser irradiation may be the basis for improving the cardiac function in patients under a course of laser therapy. Human red blood cells or isolated cell membranes were irradiated with low-intensity laser light (810 nm) at different radiant exposures (3.75-25 J/cm(2)) and light powers (fluence rate; 10-400 mW) at 37 degrees C. As the parameters characterizing the structural and functional changes of cell membranes the activities of Na(+)-, K(+)-, and Mg(2+)-ATPases, tryptophan fluorescence of membrane proteins and fluorescence of pyrene incorporated into membrane lipid bilayer were used. It was found that near-infrared low-intensity laser radiation changes the ATPase activities of the membrane ion pumps in the dose- and fluence rate-dependent manner. At the same time no changes of such integral parameters as cell stability, membrane lipid peroxidation level, intracellular reduced glutathione or oxyhaemoglobin level were observed. At laser power of 10 mW, an increase of the ATPase activity was observed with maximal effect at 12-15 J/cm(2) of light dose (18-26% for the total ATPase activity). At laser power of 400 mW (fluence rate significantly increased), inhibition of ATPases activities mainly due to the inhibition of Na(+)-, K(+)-ATPase was observed with maximal effect at the same light dose of 12-15 J/cm(2) (18-23% for the total ATPase activity). Fractionation of the light dose significantly changed the membrane response to laser radiation. Changes in tryptophan fluorescent parameters of erythrocyte membrane proteins and the increase in lipid bilayer fluidity measured by pyrene monomer/excimer fluorescence ratio were observed. Near-infrared laser light radiation (810 nm) induced long-term conformational transitions of red blood cell membrane which were related to the changes in the structural states of both erythrocyte membrane proteins and lipid bilayer and which manifested themselves as changes in fluorescent parameters of erythrocyte membranes and lipid bilayer fluidity. This resulted in the modulation of membrane functional properties: changes in the activity of membrane ion pumps and, thus, changes in membrane ion flows.

Photoresponsive Surfactants Exhibiting Unusually Large, Reversible Surface Tension Changes under Varying Illumination Conditions

We report on a new class of nonionic, photosensitive surfactants consisting of a polar di(ethylene oxide) headgroup attached to an alkyl spacer of between two and eight methylene groups, coupled through an ether linkage to an azobenzene moiety. Structural changes associated with the interconversion of the azobenzene group between its cis and trans forms as mediated by the wavelength of an irradiating light source cause changes in the surface tension and critical micellization concentrations (cmc's). Differences in saturated surface tensions (at concentrations above their cmc's) were as high as 14.4 mN/m under radiation of different wavelengths. The qualitative behavior of the surfactants changed as the spacer length changed; this behavior is attributed to the different orientations adopted by the different surfactants depending on their isomerization states. Both the azobenzene and the intermediate ether group play important roles in the control of surfactant conformation and hence surface tension.

Formation of the Diffraction Images of Extended Holes

The characteristic features of the formation of the spatial energy spectra of extended holes of millimeter cross section illuminated by radiation of different wavelengths have been investigated. The fundamental possibility of determining the diameter of an extended hole is shown. The main analytical expressions relating the radius of the hole to diffraction orders have been found.

Exposure of photosensitive glasses with pulsed UV-laser radiation

The photosensitivity in UV-range of some glasses can be used for micro structuring. The irradiated areas crystallize after a thermal treatment. Microstructures are achieved by wet-chemical etching of the crystallized areas. Interactions between UV-laser radiation of different wavelength and the photosensitive glass are investigated. The relationship between process parameters and geometry of microstructures is examined.

Photochemically Induced Reactions of Ozone with 1,2-Dibromoethene and 1,2-Dichloroethene: An FT-IR Matrix Isolation Study

The co-deposition of ozone with the halogenated ethenes, 1,2-dibromoethene and 1,2-dichloroethene, in argon matrices and the subsequent photolysis cycles using radiation of different wavelengths (λ > 350 nm, λ > 290 nm, and λ > 240 nm) have been examined using FT-IR spectroscopy. Ozonolysis occurs after irradiation at relatively long wavelengths, (λ > 350 nm), due to the formation of an ozone···XCHCHX (X = Br or Cl) π complex upon deposition and is believed to follow the Criegee pathway because the expected HC(O)X (X = Br or Cl) intermediates are detected. The carbonyl species HC(O)X dissociate to form the carbon monoxide species, OC···HX and OC···(HX)2 (X = Br or Cl). However, the identification of a novel ketene species XHCCO suggests that a further mechanism to the Criegee one is followed in the case of halogenated ethenes. Moreover the photochemically induced reaction of XCHCHX deposited in oxygen matrices produced the similar photoproducts HC(O)X and OC···HX as well as the ketene type species XHCCO, ...

Application of high-frequency contactless method of PEM investigations to examine near-surface layer of Si and GaAs

The recently reported contactless photoelectromagnetic (PEM) method of determining carrier lifetimes was used to investigate Ga : AS : Te and Si : B samples with polished and grinded surfaces. In the presented experiments the samples were illuminated with radiation of different wavelengths (and different absorption coefficients) emitted by diode lasers, argon and HeNe lasers acoustooptically modulated up to 100 kHz. The frequency dependence of PEM magnetic flux registered for cases of excess carriers photogeneration at different depths in a sample are presented and fitted with theoretical dependencies. It allows an evaluation of the bulk and near-surface region electron and hole lifetimes.

Internal photoemission characteristics of metal–insulator–semiconductor structures at low electric fields in the insulator

This article completes the presentation of a model of photoelectric phenomena taking place in metal–insulator–semiconductor (MIS) structures at low electric fields, which was introduced in Ref. [H. M. Przewlocki, J. Appl. Phys. 78, 2550 (1995)]. A solution and analysis of model’s equations is given for the general case of nonzero net photoelectric current (J≠0) in the external circuit. This solution allows calculation of the photocurrent–voltage characteristics of MIS structures illuminated with ultraviolet radiation of different wavelengths λ. To verify these results, experimental characteristics were taken and are shown in comparison with the calculated ones. Excellent agreement between calculated and experimental characteristics, obtained for a wide range of different MIS structures, strongly supports the validity of the model. Limits of applicability of this model are illustrated and discussed. The model finds applications in developing new, highly precise, photoelectric measurement methods of MIS structures. Principles of three such methods are outlined. One of these methods has already been fully verified and has been successfully used in a number of investigations, while the other two, are currently being verified and optimized.

Spectrum of the effect of laser radiation on hemoglobin of the blood vessels of skin

We suggested and consider the primary mechanism of biostimulation and of the therapeutic effect of low-level laser radiation caused by a local increase in the effectiveness of oxygen transfer by oxyhemoglobin of the blood vessels of skin. The spectra of the effect of laser radiation on oxyhemoglobin and hemoglobin of the blood vessels of skin are presented which were obtained using a method of numerical simulation with allowance for the optical characteristics of skin and for the depth of penetration into it of radiation of different wavelengths.