Optical Emission Studies Research Articles

Optical Emission Studies of Molybdenum Plasma Produced by an Nd:yag Laser

We study the optical emission characteristics of a molybdenum (Mo) plasma produced at the surface of a target material in air at atmospheric pressure using the fundamental (1,064 nm) wavelength of an Nd: YAG laser. We estimate the temperature using the Boltzmann plot method, whereas the number density is calculated using the Stark broadening profile of the neutral iron (Fe I) transition line at 538.34 nm. We investigate variations in the temperature and number density at different laser irradiance as well as the distance from the target surface along the axial direction of plasma propagation using the spectroscopic technique. We observe that the temperature and number density increase with increase in the laser irradiance.

Optical emission studies of sulphur plasma using laser induced breakdown spectroscopy

We present the optical emission studies of sulphur (S) plasma generated by the first (1064 nm) and second (532 nm) wavelengths of a Q-switched Nd:YAG laser. The target material was placed in front of laser beam in air at atmospheric pressure. The experimentally observed line profiles of neutral sulphur have been used to extract the electron temperature (T e ) using the Boltzmann plot method, whereas the electron number density (N e ) has been determined from the Stark broadening. The electron temperature is calculated by varying, distance from, the target surface along the line of propagation of plasma plume and also by varying the laser irradiance. Beside we have studied the variation of number density as a function of laser irradiance as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increases as laser irradiance is increased.

Laser-induced breakdown spectroscopic study of ammonium nitrate plasma

We present the optical emission studies of the ammonium nitrate plasma produced by the fundamental (1064 nm) and second (532 nm) harmonics of a Q-switched Nd: YAG laser. The target material was placed in front of the laser beam in an open atmospheric air. The spectrum reveals numerous transitions of neutral nitrogen. We have studied the spatial behavior of the plasma temperature (Te) and electron number density (Ne) determined using the Boltzmann plot method and Stark broadened line profiles, respectively. Besides, we have studied the variation of the plasma parameters as a function of the laser irradiance.

The quenching effect of silver nanoparticles on 2-amino-3-bromo-1, 4-naphthoquinone using fluorescence spectroscopy

Nanoparticles of noble metals belong to the most extensively studied colloidal systems in the field of nanoscience and nanotechnology. Silver nanoparticles of different sizes have been prepared with the chemical reduction method using sodium borohydride and characterized using optical absorption technique. Using optical absorption and fluorescence emission studies, the photo physical properties of 2-amino-3-bromo1, 4-naphthoquinone (ABNQ) on silver nanoparticle have been studied. Concentration of the silver nanoparticle has been evaluated and the particle size dependent interaction between silver nanoparticles and ABNQ has been studied. The fluorescence quantum yield of ABNQ with and without silver nanoparticles has been calculated. The Stern–Volmer quenching constants and the molar absorptivity have been evaluated.

Reddish-orange emission from Pr3+ doped zinc alumino bismuth borate glasses

Praseodymium doped Zinc Alumino Bismuth Borate (ZnAlBiB) glasses were prepared by melt quenching technique and characterized by optical absorption and emission studies. The glassy nature of these glasses has been confirmed through XRD spectral measurements. From the absorption spectra, the Judd–Ofelt intensity parameters Ωλ (λ=2, 4 and 6) and other radiative properties like transition probability (AR), radiative lifetimes (τR) and branching ratios (βR) have been evaluated. Emission spectra were measured for different concentrations of Pr3+ ions doped glasses by exciting the glasses at 445nm. The intensity of Pr3+ emission spectra increases from 0.1 to 1mol% and beyond 1mol% concentration quenching is observed. The suitable concentration of Pr3+ ions in ZnAlBiB glasses to act as a good lasing material at reddish-orange wavelength (604nm) region has been discussed by measuring the emission cross-sections for the intense emission transition 1D2→3H4. The CIE chromaticity co-ordinates were also evaluated from the emission spectra for all the glasses to understand the suitability of these materials for reddish-orange emission. From the measured emission cross-sections and CIE chromaticity co-ordinates, it was found that 1mol% of Pr3+ is aptly suitable for the development of visible reddish-orange lasers.

Optical emission from a small scale model electric arc furnace in 250–600 nm region

Optical emission spectroscopy has been for long proposed for monitoring and studying industrial steel making processes. Whereas the radiative decay of thermal excitations is always taking place in high temperatures needed in steel production, one of the most promising environment for such studies are electric arc furnaces, creating plasma in excited electronic states that relax with intense characteristic emission in the optical regime. Unfortunately, large industrial scale electric arc furnaces also present a challenging environment for optical emission studies and application of the method is not straightforward. To study the usability of optical emission spectroscopy in real electric arc furnaces, we have developed a laboratory scale DC electric arc furnace presented in this paper. With the setup, optical emission spectra of Fe, Cr, Cr2O3, Ni, SiO2, Al2O3, CaO, and MgO were recorded in the wavelength range 250-600 nm and the results were analyzed with the help of reference data. The work demonstrates that using characteristic optical emission, obtaining in situ chemical information from oscillating plasma of electric arc furnaces is indeed possible. In spite of complications, the method could possibly be applied to industrial scale steel making process in order to improve its efficiency.

Plasma characterization studies of laser dressing for bronze-bonded diamond wheel by a pulsed fiber laser

In this paper, we present the optical emission studies of the spatial evolution of plasma during pulsed fiber laser dressing of bronze-bonded diamond grinding wheel and especially investigate the plasma light emission, which is measured through a high sensible optical spectrometer. Space-resolved spectra in a wavelength range of 500-600 nm are measured at different laser average powers and pulse repetition frequencies, and the intensity of spectral lines achieves a maximum intensity at about 2.4 mm away from the surface of the grinding wheel. The electron temperature is determined by employing the Boltzmann plot method under the assumption of local thermodynamic equilibrium using six Cu (I) lines, and the highest electronic temperature is calculated to be 4380 K at about 3 mm away from the surface of wheel. Finally the effect of the laser parameters on the electron temperature of the plasma is studied, and the results show that there are different variation laws in the electron temperature of the plasma with laser average power and pulse repetition frequency.

Laser-based optical emission studies of barium plasma

We present the optical emission characteristics of the barium plasma produced at the surface of barium hydroxide Ba(OH)2, also known as baryta, generated by the first harmonic (1,064 nm) of a Q-switched Nd:YAG laser. The laser beam was focused on target material by placing it in air at atmospheric pressure. The experimentally observed line profiles of neutral barium have been used to extract the electron temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadening. The electron temperature is calculated by varying distance from the target surface along the line of propagation of plasma plume and also by varying the laser energy. Besides, we have studied the variation of number density as a function of laser energy as well as its variation with distance from the target surface. It is observed that electron temperature and electron number density increase as laser energy increases.

Growth of titanium nanoparticles in confined plasma

We report the growth dynamics and confinement of nanoparticles in laser ablated titanium plasma in water cavitation and air ambient. The time resolved shadowgraphs are used to analyze the shockwave, cavitations, and dynamics of expanding plume in different ambient. The dynamical growth of nanoparticles is ascertained using the laser light scattering. Temporal evolution of plasma emission spectra and its parameters show distinct characteristic difference in the plasma confined in different ambient. The morphological characteristics of synthesized nanoparticles are ascertained using electron microscopy. A comparative study of plume dynamics, light scattering and optical emission of plasma in water and air ambient is used to corroborate the nanoparticle formation.

Interfacial Electron Transfer Dynamics of Two Newly Synthesized Catecholate Bound RuII Polypyridyl‐Based Sensitizers on TiO2 Nanoparticle Surface – A Femtosecond Pump Probe Spectroscopic Study

AbstractTwo new catecholate‐bound RuII–polypyridine based sensitizers, (2,2′‐bipyridine){ethyl 3‐(4‐hydroxyphenyl)‐2‐[(4′‐methyl‐2,2′‐bipyridinyl‐4‐carbonyl)amino]propionate}{4‐[2‐(4′‐methyl‐2,2′‐bipyridinyl‐4‐yl)vinyl]benzene‐1,2‐diol)}ruthenium(II) hexafluorophosphate (5) and [(2,2′‐bipyridine)‐(4‐2,2′‐bipyridinyl‐4‐yl‐phenol)‐(4‐{2‐(4′‐methyl‐2,2′‐bipyridinyl‐4‐yl)vinyl}benzene‐1,2‐diol)]ruthenium(II) hexafluorophosphate (6) with secondary electron‐donating groups (tyrosine and phenol, respectively) were synthesized and characterized. Steady‐state optical absorption and emission studies confirm strong coupling between the sensitizers and TiO2 nanoparticles. Femtosecond visible transient absorption spectroscopy has been employed to study interfacial electron transfer (IET) dynamics in the dye–nanoparticle systems to explore the influence of the secondary electron‐donating groups on IET dynamics. Electron injection into the conduction band of nanoparticulate TiO2 has been confirmed by detection of the conduction band electrons in TiO2 ([e–]TiO2CB) and radical cation of the adsorbed dye (D·+) in real time monitored by transient absorption spectroscopy. A single exponential and pulse‐width limited (< 100 fs) electron injection has been observed. Back electron transfer (BET) dynamics have been studied by monitoring the decay kinetics of the injected electron in the conduction band of TiO2 and by the recovery of the ground state bleach. BET dynamics in dye–TiO2 systems for complexes 5 and 6 have been compared with those of [bis(2,2′‐bpy)‐(4‐{2‐(4′‐methyl‐2,2′‐bipyridinyl‐4‐yl)vinyl}benzene‐1,2‐diol)]ruthenium(II) hexafluorophosphate (7), which does not have a secondary electron‐donating group.

Robotic Astronomy and the BOOTES Network of Robotic Telescopes

The Burst Observer and Optical Transient Exploring System (BOOTES), started in 1998 as a Spanish-Czech collaboration project, devoted to a study of optical emissions from gamma ray bursts (GRBs) that occur in the Universe. The first two BOOTES stations were located in Spain, and included medium size robotic telescopes with CCD cameras at the Cassegrain focus as well as all-sky cameras, with the two stations located 240 km apart. The first observing station (BOOTES-1) is located at ESAt (INTA-CEDEA) in Mazag´on (Huelva) and the first light was obtained in July 1998. The second observing station (BOOTES-2) is located at La Mayora (CSIC) in M´alaga and has been operating fully since July 2001. In 2009 BOOTES expanded abroad, with the third station (BOOTES-3) being installed in Blenheim (South Island, New Zealand) as result of a collaboration project with several institutions from the southern hemisphere. The fourth station (BOOTES-4) is on its way, to be deployed in 2011.

Carbon nitride films by RF plasma assisted PLD: Spectroscopic and electronic analysis

Carbon nitride (CN x) thin films have been grown on Si 〈1 0 0〉 by 193 nm ArF ns pulsed laser ablation of a pure graphite target in a low pressure atmosphere of a RF generated N 2 plasma and compared with samples grown by PLD in pure nitrogen atmosphere. Composition, structure and bonding of the deposited materials have been evaluated by X-ray photoelectron spectroscopy (XPS), and Raman scattering. Significant chemical and micro-structural changes have been registered, associated to different nitrogen incorporation in the two types of films analyzed. The intensity of the reactive activated species is, indeed, increased by the presence of the bias confined RF plasma, as compared to the bare nitrogen atmosphere, thus resulting in a different nitrogen uptake in the growing films. The process has been also investigated by some preliminary optical emission studies of the carbon plume expanding in the nitrogen atmosphere. Optical emission spectroscopy reveals the presence of many excited species like C + ions, C atoms, C 2, N 2; and CN radicals, and N 2 + molecular ions, whose relative intensity appears to be increased in the presence of the RF plasma. The films were also characterised for electrical properties by the “four-probe-test method” determining sheet resistivity and correlating surface conductivity with chemical composition.

Optical emission spectra of OMCTS/O 2 fed plasmas used for thin film deposition

This paper is devoted to the optical emission studies of Octamethylcyclotetrasiloxane (OMCTS)/O 2 derived, low pressure (0.1 Torr), 13.56 MHz RF plasmas. The emission is recorded with a resolution of 0.05 nm to two RF power densities of 0.25 and 0.50 W/cm 2, at wavelengths of 180–1000 nm. Emitting atomic and molecular species in plasma are identified, and spatial variation in emission intensity is recorded through the space between electrodes. The hardness, elastic modulus, infrared absorbance, refractive index, and residual stress of the resulting plasma polymer films are presented. Most of the atomic and molecular emissions have been identified, and spectra can be used as a reference for OMCTS/O 2 plasmas. Optical emission spectra are dominated by molecular CO, CO +, OH, and CO 2 + bands, and atomic H and O lines. The absence of emissions from the Si, SiO, SiO 2, CH, CH 2, and CH 3, together with the infrared absorbance of films, suggests that SiO xC y:H film formation occurs by way of the dissociation of C–H and Si–C bonds, as well as the polymerization of silica rings or long chains.

Understanding the mechanism of nano-aluminum particle formation by wire explosion process using optical emission technique

Nano-aluminum particles are produced by a wire explosion process in different inert gas ambience. It is observed that generated particles have different sizes and it follows log–normal probability distribution. The particle size produced by the wire explosion process varies depending on the thermal conductivity of the medium and the operating pressure of the gas. To understand the mechanism of nano-particle formation, the optical-emission spectroscopic technique is used for measuring characteristics of plasma generated during the wire explosion process. Strong emission lines were observed from the species formed during the wire explosion process. Plasma temperatures are estimated based on local thermal equilibrium principle and using Al emission lines. Plasma temperature of more than 8000 K is observed in an Ar ambient. The optical emission study clearly indicates that the intensity of plasma increases with an increase in the ambient pressure. Further, it is observed that an increase in the pressure of the gas, the plasma temperature also increases. The study shows that the plasma temperature in the He gas is lesser than in the Ar gas. The plasma temperature due to the discharge plays a significant role on nano-particle formation. In addition, it is observed that irrespective of polarity, emission characteristics are almost the same.

In situ optical emission study on the role of C2 in the synthesis of single-walled carbon nanotubes

In situ optical emission spectroscopy was used to study the temporal and spatial behavior of laser induced plasmas in the laser-furnace synthesis of single-walled carbon nanotubes (SWCNTs). A graphite composite target located within a sealed quartz tube with a chemical stoichiometric composition of 95:4:1 at. wt % of carbon, yttrium, and nickel, respectively, was ablated by a Q-switched Nd:YAG laser delivering colinear, focused laser pulses of 1064 and 532 nm temporarily separated by 20 ns. The ablation process was done at a furnace temperature of 1273 K in a flow of argon gas at either 150 or 200 SCCM (SCCM denotes cubic centimeter per minute at STP). The pressure was varied (100, 400, and 600 Torr) for each gas flow setting. The temporal and spatial behavior of the emission intensity associated with C2 Swan bands (d Π3g−a Π3u) was investigated and found to be influenced by the pressure and flow rate of the argon gas. At conditions optimal to SWCNT production, a sharp drop in C2 intensity followed by a rise in C2 intensity was observed. The temporal and spatial behavior of the electron density was determined by the Stark broadening profile of the CII emission peak at 283.7 nm and was found to decrease with the adiabatic expansion of the plume. We propose that the sharp drop in C2 intensity and the rise in electron density and electron temperature observed in this study are due to the accompanying rapid nucleation and growth of SWCNTs.

Optical Emission and Raman Spectroscopy Studies of Reactivity of Low-Pressure Glow Discharges in Ar–O2 and He–O2 Gas Mixtures with Coked Catalysts

We demonstrate that low-pressure glow discharges in He–O2 gas mixture are effective in removing carbonaceous surface layers from coked catalysts. These discharges contain a number of reactive species including O, O3, and O2*, and all these could contribute in the decoking process. However, an evolving understanding is that the O atoms in the discharge have a predominant role in this. A working hypothesis is that the O atoms react with the coke to form CO, CO2 and other carbon complexes. Online measurements using emission spectra from O, H, and CO in the discharges are compared for the cases of He–O2 and Ar–O2 gas mixtures. Under the reported experimental conditions the estimated reactivity of the He–O2 discharges is considerably higher compared with discharges in the Ar–O2 gas mixture. Raman spectroscopy is used to confirm the removal of the coke from the surface of Pt/Alumina catalyst.

Optical emission studies of plasma induced by single and double femtosecond laser pulses

Double-pulse femtosecond laser ablation has been shown to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to single-pulse ablation particularly when an appropriate interpulse delay is selected, that is typically in the range of 50–1000 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy analysis of materials. A detailed comparative study of collinear double- over single-pulse femtosecond laser-induced breakdown spectroscopy has been carried out, based on measurements of emission lifetime, temperature and electronic density of plasmas, produced during laser ablation of brass with 450 fs laser pulses at 248 nm. The results obtained show a distinct increase of plasma temperature and electronic density as well as a longer decay time in the double-pulse case. The plasma temperature increase is in agreement with the observed dependence of the emission intensity enhancement on the upper energy level of the corresponding spectral line. Namely, intensity enhancement of emission lines originating from higher lying levels is more profound compared to that of lines arising from lower energy levels. Finally, a substantial decrease of the plasma threshold fluence was observed in the double-pulse arrangement; this enables sensitive analysis with minimal damage on the sample surface.

Supramolecular Donor−Acceptor Hybrid of Electropolymerized Zinc Porphyrin with Axially Coordinated Fullerene: Formation, Characterization, and Photoelectrochemical Properties

Photoelectrochemical behavior of self-assembled C60 via axial coordination to an electrochemically polymerized zinc porphyrin film was systematically investigated to unravel the importance of the coordinated fullerene in improving the photocurrent and photovoltage generation of the resulting donor−acceptor dyad. For this, tetrakis(4-(N,N-diphenylamino)-phenyl)porphyrinato-zinc(II), (Ph2N)4ZnP, bearing electropolymerizable triphenylamine peripheral substituents was first electropolymerized to form a film on the electrode surface. The resulting formation of the electrochemically active and dense film was confirmed by using an electrochemical quartz crystal microbalance (EQCM) and by atomic force microscopy imaging. The optical absorption and emission studies revealed the characteristic absorption and emission bands of zinc porphyrin that suggested preservation of the π-electron system of the porphyrin monomer in the polymer. Further, the fullerene, derivatized with an axially coordinating imidazole ligand, was allowed to self-assemble via axial coordination to the zinc center of the (Ph2N)4ZnP polymer film. The simultaneously performed piezoelectric microgravimetry and cyclic voltammetry studies using EQCM allowed us to prove this coordination and to evaluate the redox potential of the donor, (Ph2N)4ZnP, and acceptor, C60, moiety. The fluorescence emission results, along with the free energy calculations, suggested the occurrence of vectorial photoinduced electron transfer from the singlet-excited ZnP in the polymer to the axially coordinated fullerene moiety. Systematic photoelectrochemical studies revealed cathodic photocurrent generation, a result unlike most of the dye-sensitized photoelectrochemical cells reported in the literature. Moreover, the coordinated fullerene to the zinc porphyrin film improved the photocurrent and photovoltage generation of the photoelectrochemical cell. An incident photon-to-current conversion efficiency (IPCE) of nearly 2% at the Soret region of maximum absorption was determined for the [(Ph2N)4ZnP polymer]−fullerene hybrid film.

C 2 and CN dynamics and pulsed laser deposition of CNx films

The time-resolved optical emission studies of laser ablated carbon plasma in nitrogen ambient are carried out to understand the dynamic of formation of C2 and CN for depositing quality thin films. An optimum formation of C2 is observed at 3 mm from the target surface and 350 ns after the initiation of plasma. However, CN is formed at comparatively larger distance, 4 mm, and larger delay (850 ns). The expanding plasma plume splits/bifurcates into slow and fast moving two distinct components, with the faster components further splitting up at later times (>350 ns) into two components. The estimated plume front velocity from plume imaging in the nitrogen ambient of 1.2 mbars at a delay of 100 ns is 3.8×106 cm/s, consistent with spectroscopic measurement ∼3.0×106 cm/s. The CNx thin films deposited by pulsed laser deposition technique are characterized by x-ray diffraction, atomic force microscopy, and Raman spectroscopy. The high ID/IG ratio and peak position shift of G band to lower values in the films deposited for longer time indicates the high incorporation of nitrogen and increasing CN concentration within the film.

Ferromagnetism and Near-infrared Luminescence in Neodymium and Erbium Doped Gallium Nitride via Diffusion

AbstractIn this study, we report on the diffusion of neodymium (Nd) and erbium (Er) into n-type and undoped GaN and subsequent measurements of the room-temperature (RT) magnetic and optical properties. The diffusion profile has been measured via secondary ion mass spectroscopy (SIMS) with rare-earth (RE) concentration yields of up to 1×1018/cm3. The ferromagnetic properties were measured using an alternating gradient magnetometer (AGM) giving a saturation magnetization (Ms) of up to 3.17emu/cm3 for the RE-diffused layer. The photoluminescence (PL) emission of the Nd-diffused and Er-diffused GaN is observable in the near-infrared (NIR) and infrared (IR) regions of the spectrum, respectively. The Nd-diffused GaN samples show NIR emission at 1064nm and 1350nm, while Er-diffused GaN samples have IR emission at 1546nm. This appears to be the first successful result of Nd diffusion doping into GaN crystals, and the first demonstration of above RT ferromagnetism involving GaN diffused with Nd. Details of our ferromagnetic and optical emission studies, related to the RE diffusion into GaN, are presented.