Spectral characteristics of luminescent emission of negatively charged nitrogen-vacancy (NV–) centers in synthetic diamonds while filling of lower spin sublevels by microwave radiation were studied. On recorded spectra secondary side spin resonances induced by the hyperfine interaction between the NV– center electronic spin and the 13C nuclear spin were found out on the frequencies of 2.8136 GHz and 2.9408 GHz.
Using optical spectroscopy in the spectral range from 200 to 300 nm, the absorption edge and transmission spectra of 7 samples of synthetic diamond of IIa type in the temperature range from 12 K to 470 K was studied. Using numerical methods, the temperature dependences of optical absorption into the free exciton state were obtained for negative and positive phonon branches.
The study of exciton cathodoluminescence in diamond is not only scientific but also practical importance. Ultraviolet radiation at a wavelength of 235 nm can be used for disinfection, activation of surface reactions, photochemistry, and more. Thus, diamond is a promising material for creating a cathodoluminescent source of ultraviolet radiation. We have investigated the temperature dependences of the exciton cathodoluminescence spectra of single-crystal diamond in the temperature range from 80 to 400 K. The temperature dependences showed a characteristic increase in the intensity of exciton cathodoluminescence in the range 230-240 nm with increasing temperatures from 80 K to 150- 180 K. Further increase in temperature to room temperature (297 K) leads to a twofold decrease in the radiation intensity. With a further increase in temperature to 400 K, no change in the cathodoluminescence intensity was observed within the error
The paper presents the results of studies of the effect of single presowing treatment of wheat seeds with XeCl excilamp radiation at 308 nm with various surface irradiation doses on the yield and seed quality of spring wheat of the Iren variety, obtained in 2018 in the Tomsk.
The paper presents measurement data on the radiation excited in synthetic diamonds, leucosapphire, and quartz KU1 at a wavelength of 200–800 nm by a pulsed electron beam with an energy of up to 400 keV. The crystals reveal wide bands whose intensity increases with decreasing wavelength in the range 220–400 nm. For leucosapphire and quartz, the radiation pulse at these wavelengths is close in duration to the electron beam current pulse, suggesting that it is Cherenkov radiation. For synthetic diamonds, both Cherenkov radiation and pulsed cathodoluminescence are detected in this spectral region. In particular, an intense band of free excitons with its maximum at 235 nm is found at high beam current densities and electron energies.
Optical absorption spectra in the temperature range of 85-300 K and IR absorption spectra at room temperature of four diamond samples were studied. All samples demonstrated the GR1 vibronic system of a neutral vacancy. The absorption coefficient at the zero-phonon line at 1.673 eV decreased by the power law in the temperature range of 120-230 K. Outside this temperature range, the absorption on the neutral vacancy did not practically changed. The value of the absorption coefficient at the neutral vacancy correlated well with the densities of nitrogen impurity-defective NV-, N2Vand N4V-complexes.
The study of optical absorption of CVD diamond near the fundamental absorption edge was performed in the temperature range of 87-296 K. At temperatures lower than 195 K the absorption was practically constant. At higher temperatures the sharp increase of absorption took place. This sharp increase was attributed to the sharp enrichment of the phonon spectrum. Same phonon modes have different contributions to the negative and the positive branches of freeexciton absorption. For the negative branch (phonon absorption) the TA-mode dominated. For the positive branch (phonon emission) the TO-mode dominated. The possibility of diamond-based cathodoluminescent UV-sources at 235 nm was demonstrated.
The cathodoluminescence spectra of nine diamond samples at temperatures of 82-295 K were investigated. According to the presence of the N3a vibronic system with the zero-phonon line at 2.68 eV in the luminescence spectra, six samples were identified as natural. By the presence in the luminescence spectra of the 2.56-eV vibronic system and the unstructured band at 2.54 eV, associated with nickel, two samples were identified as synthetic, grown at high pressure and high temperature. Due to exciton luminescence at 5.271 eV and the absence of any spectral features of impurity nature, one sample was identified as synthetic, grown by the chemical vapor deposition. Based on the data obtained, the technique for identifying of natural and synthetic diamonds has been proposed.
The inactivation of eggs of Opisthorchis felineus and Diphyllobothrium latum in the water under the action of UV excilamps at 222 and 282 nm in dependence on the surface dose of radiation was studied. It was observed that the water disinfection from eggs of helminthes was more efficient at 222 nm, than at 282 nm. At the surface dose up to 5 mJ/cm2 of UV radiation at 222 nm up to 85 % of Opisthorchis felineus eggs were inactivated. At the comparable surface dose of UV radiation at 222 nm up to 56 % of Diphyllobothrium latum eggs were inactivated.
Integrated photoluminescence spectra of two diamond samples under laser radiation excitation at 193 and 222 nm, depending on the temperature in the range of 80-300 K and the peak intensity in the range of 7-13 MW/cm2, were investigated. At temperatures below 200 K, and the peak intensity of more than 10 MW/cm2 of laser radiation at 222 nm, the radiative recombination band of electron-hole liquid was observed in integrated photoluminescence spectra of CVD diamond sample.
In our work we investigated different optical characteristics of five diamond samples that were supposed to be pure. The characteristics were the following: optical absorption spectra in the range 200 nm – 15μm, Raman scattering spectra in the range 100-3700 cm-1 and photoluminescence spectra in the range 200 – 850 nm. The temperature of diamond samples was varied from 80 to 300 K. Photoluminescence was excited by KrCl*-laser radiation (λ=222 nm) with pulsewidth of 8 ns (FWHM) and peak intensity of 13 MW/cm2. We found out that the band of radiative recombination of the electron-hole liquid (with the maximum at 240 nm) can be observed in the photoluminescence spectra if the absorption coefficient of the diamond sample is less than 10 cm-1 in the range 225-226 nm.
Photoluminescence and optical transmission spectra of several samples of natural and synthetic diamond and its
imitators - fianite and corundum - are investigated. The band-A of luminescence at 440 nm, the vibronic N3 system of
luminescence and absorption at 415.2 nm, the fundamental absorption edge at 225 nm, and the secondary absorption
below 308 nm are the main identifying markers of natural diamonds. For synthetic diamonds, however, such identifying
markers are the exciton luminescence at 235 nm, the band-A, and the fundamental absorption edge. Fianites can be
identified by the structureless wide band at 500 nm and the wide transmission band in the entire visible range. Colored
corundum samples with chrome impurities emit the narrow line at 693 nm and show the absorption band in the 500-600
nm spectral range. A new method for diamond express identification is developed on the basis of measurement of
photoluminescence and optical transmission spectra of the samples. It is shown that a diamond tester can be designed
combining a spectrometer and a KrCl-excilamp radiating at 222 nm.
Transmission and luminescence spectra of natural or/and synthetic samples of corundum, diamonds and phianites are
obtained by irradiation of a KrCl-excilamp (222 nm) driven by the barrier discharge. It is offered to use a KrCl-excilamp
for development of devices for nondestructive identification of diamonds and their imitations.
The studies of luminescence of synthetic ruby, natural spodumene and natural IIa type diamond under the action of laser radiation at 222 nm and subnanosecond avalanche electron beam (SAEB) were carried out. It was demonstrated that SAEB parameters allow obtaining high-intensity luminescence of various crystals in the normal conditions without any vacuum equipment used. At the both types of excitation, ruby emission spectra were similar demonstrating luminescence of chrome only. It was shown that photoluminescence spectra of the spodumene and diamond samples contained some bands being absent in SAEB-initiated cathodoluminescence spectra.
At e-beam duration of 2-20 ns a shift of free-exciton line to the high-energy area in a pulsed cathodoluminescence spectrum of CVD diamond was observed. Such a shift had the higher value at the shorter e-beam duration. At ≈ 2 ns e-beam and a room temperature the free-exciton line was observed at 5.312±0.009 eV with the corresponding energy of wavevector-conserving phonon close to the energy of transverse acoustic phonon.
Diamond radiation detectors (DRDs) operate on the principle of photoconductive response of the normally insulating, Type IIa diamond when dosed by electromagnetic radiation or high energy particles. As detectors, they offer fast response (~100 ps) and can handle high radiation doses (~1 GGy) without degradation. Diamond also offers significant advantages over semiconducting materials as a compact, bi-polar, high voltage switching medium because of its high dielectric strength and thermal conductivity. However, the wide band-gap of diamond and its normally insulating state impose stringent requirements on the trigger radiation that is used to make the diamond conductive. This paper describes a simple model for conduction in diamond, and compares this model with experimental conductivity as measured in a natural diamond Type IIa radiation detector that was irradiated by laser excitation at various wavelengths from 222-353 nm. The DRD geometry consisted of a 3x1x0.5 mm3 Type IIa diamond with metallization on the 3x0.5mm2 sides. The DRD was exposed to laser light in the orthogonal 3x1 mm2 plane. Agreement with the measured data is achieved by fitting a parameter (defined here as β) at the various irradiation wavelengths. This fitting parameter is itself a function of two physical quantities: α, the absorption coefficient of the diamond and εo, the ionization cost to produce a hole-pair. Using published values of α, we deduce values of εo and compare them with published values for Type IIa diamond in the deep UV to soft x-ray regions. This model also provides a basis for design of high voltage diamond switches that are triggered by near-bandgap (220-250 nm) UV radiation.
Investigation of the modes of thin metal and ceramic films (0,3-1 μm) removal from the glass and stainless steel substrate by IR and UV laser radiation has been performed. It is presented that the efficient film destruction and removal occurs due to laser induced thermal strength under laser fluxes of ~0.5 J/cm2 not sufficient for phase transformation.
The interaction of Xe- (λ~1.73 µm) and XeCl- (0.308 μm) lasers radiation with surfaces of metal and TiN-ceramic coatings on glass and steel substrates has been studied. Correlation between parameters of surface erosion (area of crater and amount of evaporated material versus laser focus position and number of pulses) was investigated. Monitoring of laser induced erosion on smooth polished surfaces was performed using optical microscopy. The correlation has been revealed between characteristic zones of thin coatings damaged by irradiation and energy distribution over laser beam cross section allowing evaluation of defects and adhesion of coatings.
Presently, from the world data available on interaction of laser radiation with metal and dielectric surfaces and development of experimental diagnostic techniques by itself it is possible to raise a reverse question, namely, restoration of laser radiation energy spatial distribution through surface imprint. With this in mind, we have made the detailed morphology of imprint of a pulse HF-laser interaction with carbon steel surface through atomic force microscope. Interaction of the radiation of a relatively short pulse of ArXe-laser ((tau) ½equals400 ns, (lambda) equals1,73 micrometers , Q ~ 20 J/cm+2)) with carbon steel surface of 40X (4140 (USA)) type besides the surface layer hardening leaded to decrease of steel hardness at below original value on depth of about 10 - 12 micrometers . This effect can be related to occurrence of deformation and thermal residual stresses in the subsurface layer. At multiple-pulse interaction (~500 pulses) of UV-laser focused radiation ((lambda) equals0,222 or 0,308 micrometers , (tau) ½equals 12 or 20 ns) with the steel 40X (4140 (USA)) surface a distinct interference imprint of laser beam is formed after diffraction at outer diaphragm being determined by its form.
Phenol and 4-chlorophenol water solutions photolysis under UV-excitation from KrCl-laser and capacitive discharge KrCl- excilamp are presented. The irradiated solutions have been investigated by spectroscopic methods. The comparison of the KrCl-excilamp and KrCl-laser irradiation effects has been realized for the first time.
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