Synthesis of nanoparticles using a pulsed electrical discharge in a liquid

We used a pulsed electrical discharge in a liquid to obtain Cu-, WC-, and ZnO-containing nanoparticles. The effect of the discharge current and pulse duration on the morphology and phase composition of the synthesized material was studied by spectrophotometry, transmission electron microscopy, and x-ray diffraction analysis. We discuss possible mechanisms for nanoparticle formation in a discharge submerged in a liquid. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 111–120, January–February, 2008.     

Laser initiation of a mixture of PETN with NiC nanoparticles at elevated temperatures

The temperature dependence of the probability of the explosion of pentaerythritol tetranitrate (PETN) with an admixture of NiC particles (0.3 wt %) initiated by laser pulses (1064 nm, 20 ns) was studied over the temperature range 295–450 K. At 295–350 K, a weak temperature dependence was observed. The determining contribution to explosion initiation was made by the absorption of laser radiation by nanoparticles. The threshold of explosive decomposition at 295 K decreased by ∼40 times compared with samples free of NiC nanoparticles. Over the temperature range 400–450 K, the threshold of the explosive decomposition of samples containing NiC nanoparticles decreased with the activation energy ∼0.4 eV. A decrease in the threshold of explosive decomposition with a ∼0.4 eV activation energy over the temperature range 340–440 K was also observed for laser action on PETN samples not containing NiC. A hypothesis was suggested according to which the absorption of a light quantum caused the transfer of an electron from the valence band of the crystal to a level in the forbidden band with subsequent thermal positive ion dissociation to the carbocation and NO₃ radical.     

X-ray generation in low-voltage vacuum discharges

The dynamics of x-ray emission from a low-voltage laser-induced discharge was studied with the aid of a picosecond x-ray streak camera. Directed x-ray emission in the spectral range from 100 eV to 10 keV in the form of point sources and thin layers with lifetimes ranging from 30 ps to 1 ns was observed in a low-voltage vacuum discharge (U=150 V) initiated by a picosecond laser beam. X-ray emission from a discharge was detected with a time delay (1–20 ns) relative to ignition by the laser beam in order to prevent the radiation of the laser plasma from entering the detector. Detection of directed x-ray emission in a low-voltage vacuum discharge is demonstrated. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 9, 622–627 (10 May 1998)     

Low-Noise single-frequency He-Ne laser with stable output power at a wavelength of 1.52 µm

The results of investigation of the energy and spectral characteristics of a He-Ne laser (λ_rad=1.52 μm) with transverse microwave discharge are presented. A single-frequency generation mode at a pressure above 6.0 mm Hg was obtained with radiation power 7.0 mW and low level of amplitude noise (10⁻⁵ Hz^−1/2). Active stabilization of the laser power was carried out, which allows reduction in radiation intensity fluctuations from 1–5 to 0.1 %. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 127–128, January–February, 2000.     

Intense XUV emission generated by a capillary discharge based apparatus

We present the characterization of an apparatus generating XUV radiation by a high peak value (20–40) kA and short rise time (≈ 20 ns) current pulse in a capillary discharge channel (up to 20 cm in length) filled by argon gas. The apparatus has been developed with the purpose of production of an intensive spontaneous emission in the spectral region of (2–50) nm and study of the z-pinch conditions for obtaining the laser generation in the Nelike Ar at 46.9 nm. The current pulses are generated by the direct discharge of a 7 nF water dielectric capacitor resonantly charged up to 400 kV by a six-stages Marx generator. The XUV radiation emitted during the radial compression of the plasma column is measured using calibrated PIN diodes, filters and multilayer mirrors in order to test the z-pinch plasma collapse and to measure the conversion efficiency of the electrical energy into the XUV radiation. This work is supported by the Italian National Institute of Nuclear Physics and in part by the Italian National Institute of Matter Physics.     

Stimulated Raman conversion of radiation from a YAG:Nd laser with wavelengths of 1.319, 1.338, and 1.357 µm in a barium nitrate crystal

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M₂ = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 μm, 1.338 μm, and 1.357 μm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 μm, 1.556 μm, and 1.582 μm with divergence of the beams of converted radiation close to the diffraction-limited value (M₂ < 1.5). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 330–334, May–June, 2006.     

Source of far and vacuum ultraviolet radiation based on a transverse high-frequency discharge

We present the results of an investigation of a short-wavelength radiation source (Δλ = 130–350 nm) with excitation by a transverse high-frequency (f = 1.76 MHz) discharge based on a mixture of argon and chlorine (p = 100–500 Pa). We have studied the spectral characteristics of the plasma, the oscilloscope traces of the voltage, the current and emission of the discharge, the dependence of the power of the emission on the electrical power of the discharge, and also the pressure and partial composition of the Ar/Cl₂ mixture. The UV-VUV source emits in a system of broadened and overlapping ArCl(B/X), Cl₂(D′/A′), and Cl**₂ molecular bands. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 648–651, September–October, 2007.     

Optical characteristics of a transverse discharge in neon at atmospheric pressure

We present the results of investigation into radiation of a pulsed transverse discharge in neon at a pressure of 10–200 kPa. Survey spectra of plasma radiation, time characteristics of radiation, and the effect of small impurities of water vapors and air on the optical characteristics of a neon plasma were studied. We show that at a pressure of residual gases at a level of 10 Pa intense OH*, NO*, and N _* ² bands are observed in radiation of the plasma of a nanosecond transverse discharge in Ne against the background of continuous plasma radiation, and in the spectral region with λ>400 nm radiation was observed on the H_β 486.1 nm and NeI 585.3 nm lines, and (when P≥100 kPa) on the line at the 3s–3p-transitions of a Ne atom. The radiation intensity of the third continuum of neon increases with pressure and with energy contribution to plasma, with its maximum being located in the VUV spectral region (λ _max <200 nm). To whom correspondence should be adressed. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 5–10, January–February, 1999.     

Metal-on-oxide nanoparticles produced using laser ablation of microparticle aerosols

A continuous aerosol process has been studied for producing nanoparticles of oxides that were decorated with smaller metallic nanoparticles and are free of organic stabilizers. To produce the oxide carrier nanoparticles, an aerosol of 3–6 μm oxide particles was ablated using a pulsed excimer laser. The resulting oxide nanoparticle aerosol was then mixed with 1.5–2.0 μm metallic particles and this mixed aerosol was exposed to the laser for a second time. The metallic micron-sized particles were ablated during this second exposure, and the resulting nanoparticles deposited on the surface of the oxide nanoparticles producing an aerosol of 10–60 nm oxide nanoparticles that were decorated with smaller 1–5 nm metallic nanoparticles. The metal and oxide nanoparticle sizes were varied by changing the laser fluence and gas type in the aerosol. The flexibility of this approach was demonstrated by producing metal-decorated oxide nanoparticles using two oxides, SiO₂ and TiO₂, and two metals, Au and Ag.     

Single-frequency regime of oscillation of a high-power He—Ne laser with a transverse SHF discharge

The possibility of producing a single-frequency regime of oscillation of a He−Ne laser with a transverse shf discharge by changing the pressure of the gas mixture is investigated. A single-frequency regime of oscillation with a high radiation power (10 mW) and a low level of amplitude noise (10⁻⁵ Hz^−1/2) has been produced at a pressure above 6 mm Hg. The laser power in the single-frequency regime comprises 60–80% of the power in the regime of multifrequency oscillation. Physics Department, Tashkent State University, Campus, Tashkent, 700095, Uzbekistan. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 116–118, January–February, 1997.     

Photoinduced optical activity of C<Subscript>70</Subscript> fullerene in organic solvents

We have experimentally studied for the first time the effect of photoinduced rotation of the plane of polarization for pulsed laser radiation in solutions of C₇₀ fullerene in organic solvents and their mixtures. We have shown that the effect is observed for elliptical polarization of the laser radiation and is absent for linear polarization. We present the results of a study of the nonlinear optical characteristics of the C₇₀ solutions. We discuss the physical mechanisms by which nonlinear gyrotropy is induced in solutions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 93–99, January–February, 2009.     

Formation of conical microstructures upon laser evaporation of solids

The formation and development of the large-scale periodic structures on a single crystal Si surface are studied upon its evaporation by pulsed radiation of a copper vapor laser (wavelength of 510.6 nm, pulse duration of 20 ns). The development of structures occurs at a high number of laser shots (∼10⁴) at laser fluence of 1–2 J/cm² below optical breakdown in a wide pressure range of surrounding atmosphere from 1 to 10⁵ Pa. The structures are cones with angles of 25, which grow towards the laser beam and protrude above the initial surface for 20–30 μm. It is suggested that the spatial period of the structures (10–20 μm) is determined by the capillary waves period on the molten surface. The X-ray diffractometry reveals that the modified area of the Si substrate has a polycrystalline structure and consists of Si nanoparticles with a size of 40–70 nm, depending on the pressure of surrounding gas. Similar structures are also observed on Ge and Ti. Received: 12 February 2000 / Accepted: 28 March 2000 / Published online: 20 June 2001     

Passive Q-switching of erbium glass laser by magnesium aluminosilicate sitall with cobalt ions

We have studied the radiation output parameters for an erbium glass laser, lasing at a wavelength of 1.54 μm, with passive Q-switching by means of a cobalt-containing magnesium aluminosilicate sitall compared with a saturable absorber based on a magnesium aluminum spinel crystal with cobalt ions. We have shown that the output characteristics of the laser emission when using sitall are not inferior to the analogous characteristics of a laser based on a spinel crystal, and are practically independent of the temperature of the saturable absorber in the range 0°C–80°C. The duration (energy) of the output pulses was 70 nsec (∼4 mJ), the energy dispersion of the radiation pulse relative to the average value was no greater than 3%, the beam divergence was 2.8 mrad, the laser beam quality factor was M² = 1.2. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 126–131, January–February, 2007.     

Structure of Fe–Pt alloy included carbon nanocapsules synthesized by an electric plasma discharge in an ultrasonic cavitation field of liquid ethanol

For the first time Fe–Pt alloy included carbon nanocapsules were synthesized by an electric plasma discharge in an ultrasonic cavitation field of liquid ethanol. This contrasts the extensively used chemical synthesis methods which produce uncoated Fe–Pt alloy nanoparticles. We proposed that the as-synthesized Fe–Pt alloy included carbon nanocapsules are potentially useful in biomedical applications. Thereby an aim of this work was to coat the Fe–Pt alloy nanoparticles by graphite shells using plasma discharge in liquid ethanol and to study the structure and magnetic properties of the carbon encapsulated Fe–Pt alloy nanoparticles. The core–shell structured nanoparticles were characterized by transmission electron microscopy and X-ray diffraction. These methods revealed the presence of a disordered face-centered cubic (fcc) structure (γFe, Pt) in the cores of the as-synthesized carbon nanocapsules. The as-synthesized carbon nanocapsules showed the soft magnetic character at room temperature. These carbon nanocapsules may provide a new approach in the transport and delivery of anticancer drugs.     

Determination of carbon in soil by laser spectral analysis

We have used a combination laser/electrospark method for fast determination of carbon content in soil. Excitation of the spectra is carried out both directly in a laser ablation plume and when a pulsed electric discharge is applied to it. We have plotted a calibration curve that is linear for the major concentration range of practical importance for the analyte element, all the way up to 8.6%. The carbon detection limit for the combination discharge approach is 0.07%. We have analyzed the ratio of the nitrogen and carbon contents, and also the hydrogen and carbon contents as a function of the carbon concentration in the studied soils samples. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 262–268, March–April, 2008.     

Calculation of the parameters of excimer light sources on the basis of a positive column glow discharge

We calculate the concentration of plasma and gas-temperature components in a contracted filament of a glow capillary discharge (R = 0.75 mm) in xenon for pressures of P = 100 and 400 Torr and currents of I = 6–15 mA for cases of with and without cryogenic cooling of the discharge. We find that the gas temperature in the channel of the glow discharge has a value of 1000–2000 K, the concentration of xenon excimers attains a maximum at the boundary of the filament with a value of 10¹⁰–10¹¹ cm⁻³, and the efficiency of electric energy transformation into excimer radiation energy has a value of 0.1–5%.     

Plasma synthesis and treatment of nanosized chalcopyrite particles

We synthesized chalcopyrite (CuFeS2) nanoparticles by methods involving laser ablation and electrical discharge in water. The nanoparticles obtained were exposed to an oxygen/argon plasma of a microwave discharge. The synthesized material was studied by photometry, x-ray diffraction (XRD), and energy dispersive x-ray elemental analysis (EDX), IR spectroscopy, and atomic force electron microscopy (AFM). We have established that the nanoparticles are morphologically stable relative to exposure to plasma fluxes of power ≤1 kW, and can be used as a model system to study processes of interaction between a plasma and minerals.     

Nanoparticle diffusion probing of the structure of water and aqueous organic solutions near a porous surface and in its bulk in a wide temperature interval

Scattering of laser radiation by nanoparticles (latex balls and silver nanoparticles) is investigated in a wide temperature interval. It is demonstrated that water is structured near the porous surface of a solid body and acquires low-dimension topology coinciding with the fractal dimension of the porous surface. A correlation is established between variations in the nanoparticle diffusion coefficient and the dielectric properties of aqueous organic solutions with an organic component in the mixture. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 8–15, February, 2009.     

Intracavity parametric conversion of radiation from a pulsed Nd:YVO<Subscript>4</Subscript> laser with high-power diode pumping

We have achieved intracavity parametric conversion of the radiation from a laser based on Nd:YVO₄ with high-power diode pumping. An LiF^2- crystal was used as the passive Q-switch for the Nd:YVO₄ laser. We have shown that by using an active element in the master laser with a passive region, we can form pulsed laser beams at a wavelength of 1.57 μm with peak power 3.2 kW and repetition rates up to 80 kHz, with beam quality parameter 1.4–1.8. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 5–8, January–February, 2006.     

Laser fabrication of periodic microstructures from silver nanoparticles in polymer films

The fabrication of photoand thermostable periodic structures from silver nanoparticles in polymer plates (cross-linked oligourethanemethacrylate impregnated with silver precursors Ag(hfac) and Ag(fod) dissolved in the supercritical carbon dioxide) is studied. The process is based on the local (depending on the irradiated spot size) photochemical decomposition of the silver precursors in the polymer matrix that initiates the atomic aggregation and creation of silver nanoparticles with the plasmon resonance in absorption in the spectral range 420–430 nm. The third-harmonic radiation of a Nd:YAG laser (355 nm) and the Kr⁺-laser (521 nm) radiation are employed for the recording of periodic structures with submillimeter and micron resolutions. The photosensitivity of the polymer matrices impregnated with the silver precursors to the UV and visible radiation is discussed.