Laser plasma plume kinetic spectroscopy of the nitrogen and carbon species (original) (raw)
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Optical probe investigation of laser ablated carbon plasma plume in nitrogen ambient
Physics of Plasmas, 2013
We report the study of carbon plasma produced using 1064 nm laser in nitrogen ambient at atmospheric pressure using 2-dimensional fast imaging of ablated plume, optical emission spectroscopy, and optical probe at 532 nm for interferometry and shadowgraphy. The dominance of C 2 and CN molecules over ionic species at later stages of expanding carbon plasma plume is reported. The observed ring structure in shadowgrams and change in the direction of fringe shift from positive to negative in recorded interferograms are correlated with the relative abundance of different species in the plasma plume as function of time delay with respect to ablating pulse. An agreement in observed onset time of formation of clusters/atomic species or low ionic species using different diagnostic techniques has been reported. V
Interaction of ambient nitrogen gas and laser ablated carbon plume: Formation of CN
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
Pulsed laser ablated carbon plasma in a nitrogen background gas in the pressure range from 10 mTorr to 100 Torr is investigated by optical emission spectroscopy using 1.064 and 0.355 lm laser wavelengths. C 2 and CN emission bands dominated the emitted spectrum at all ambient gas pressures at low incident laser intensity commonly used for pulsed laser deposition of thin films. The light intensity of C 2 and CN band heads is highly dependent on laser wavelength, laser energy, and ambient gas pressures. Emission from N þ 2 was detected at all nitrogen pressures. N I and N II are also observed in the emitted spectrum at the background gas pressure greater than 1 Torr. The vibrational temperature of CN species is found to be greater than that of C 2 species. The mechanism of formation of C 2 and CN molecules is discussed.
Optical spectroscopy of emission from CN plasma formed by laser ablation
Physica Scripta, 2008
The characterization of a plasma plume is a key issue in laser ablation and deposition studies. The formation, composition and propagation of laser-produced plasmas used for pulsed laser deposition (PLD) of CN have been studied under film growth conditions. The plume was generated by focusing 1064 nm, 9 ns pulses from Nd:YAG laser on carbon target under nitrogen ambient. We investigated the different species, such as CII, CI, C 2 , NII and CN, in laser ablated CN plasma using optical emission spectroscopy. The spectral characteristics of the plasmas were measured to determine the plasma properties as gas pressure was changed from 10 −5 to 90 mTorr. The intensities of molecular species did not depend on gas ambient whereas ion intensities did. The vibrational temperature shows dependence with gas pressure.
Atoms
In this study, we examine the atomic and molecular signatures in laser-induced plasma. Abel inversions of measured line-of-sight data reveal insight into the radial plasma distribution. Laser-plasma is generated with 6 ns, Q-switched Nd:YAG radiation with energies in the range of 100 to 800 mJ. Temporally- and spatially-resolved emission spectroscopy investigates expansion dynamics. Specific interests include atomic hydrogen (H) and cyanide (CN). Atomic hydrogen spectra indicate axisymmetric shell structures and isentropic expansion of the plasma kernel. The recombination radiation of CN emanates within the first 100 nanoseconds for laser-induced breakdown in a 1:1 mole ratio CO2:N2 gas mixture. CN excitation temperatures are determined from fitting recorded and computed spectra. Chemical equilibrium mole fractions of CN are computed for air and the CO2:N2 gas mixture. Measurements utilize a 0.64-m Czerny–Turner type spectrometer and an intensified charge-coupled device.
Carbon-plasma produced in vacuum by 532nm–3ns laser pulses ablation
Applied Surface Science, 2006
A study of VIS laser ablation of graphite, in vacuum, by using 3 ns Nd:YAG laser radiation is reported. Nanosecond pulsed ablation gives an emission mass spectrum attributable to C n neutral and charged particles. Mass quadrupole spectroscopy, associated to electrostatic ion deflection, allows estimation of the velocity distributions of several of these emitting species within the plume as a function of the incident laser fluence. Time gated plume imaging and microscopy measurements have been used to study the plasma composition and the deposition of thin carbon films. The multi-component structure of the plume emission is rationalized in terms of charge state, ions temperature and neutrals temperature. A special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated in the non-equilibrium plasma conditions. The use of nanosecond laser pulses, at fluences below 10 J/cm 2 , produces interesting C-atomic emission effects, as a high ablation yield, a high fractional ionization of the plasma and presence of nanostructures deposited on near substrates. #
Kinetic modeling study of the laser-induced plasma plume of cyclotrimethylenetrinitramine (RDX)
Spectrochimica Acta Part B: Atomic Spectroscopy, 2007
A kinetic model of a laser-induced breakdown spectroscopy (LIBS) plume of cyclotrimethylenetrinitramine (RDX) was developed for the analysis of processes responsible for the LIBS signature of explosives. Air and argon were considered as buffer gases. The model includes a set of processes involving ion chemistry, as well as excitation, ionization, and other processes affecting neutral and ion species. Modeling results show that the overall reaction process can be considered a two-stage process. The first stage corresponds to a fast approach to a quasi-stationary state, while the second stage corresponds to the change of quasi-stationary species concentrations due to the change in temperature. As a result of the two-stage process, the initial mechanism of explosive decomposition is not important in determining its signature in the LIBS measurement time window (1-30 μs). The main processes responsible for generation of excited states for the LIBS emission are electron-excitation impact processes. A mechanism for the appearance of a double peak of the C 2 species concentration in the RDX plasma plume was suggested. Double-peak behavior of the C 2 species was previously experimentally observed during laser ablation of graphite. Published by Elsevier B.V.
This work examines atomic and molecular signatures in laser-induced plasma in standard ambient temperature and pressure environments, including background contributions to the spectra that depend on the laser pulse-width. Investigations include solids, gases, and nano-particles. Abel inversions of measured line-of-sight data reveal insight into the radial plasma distribution. For nominal 6 nanosecond laser pulses and for pulse-energies in the range of 100 to 800 mJ, expansion dynamics and turbulence due to shock phenomena are elucidated to address local equilibrium details that are frequently assumed in spatially averaged emission spectroscopy. Chemical equilibrium computations reveal temperature dependence of selected plasma species. Specific interests include atomic hydrogen (H) and cyanide (CN). Atomic hydrogen spectra indicate axisymmetric shell structures and isentropic expansion of the plasma kernel over and above the usual shockwave. The recombination radiation of CN emanates...
Journal of Physics D: Applied Physics, 2008
Optical emission spectroscopy studies, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO 2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm −2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C + , C 2+ and C 3+ and molecular features of C 2 (d 3 g-a 3 u ; Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C 4+ and molecular features of C 2 (E 1 + g-A 1 u ; Freymark system), C 2 (D 1 + u-X 1 + g ; Mulliken system), CN(D 2-A 2), C 2 (e 3 g-a 3 u ; Fox-Herzberg system), C 2 (C 1 g-A 1 u ; Deslandres-d'Azambuja system), OH(A 2 +-X 2), CH(C 2 +-X 2), NH(A 3-X 3 −), CN(B 2 +-X 2 + ; violet system), CH(B 2 +-X 2), CH(A 2-X 2), C 2 (A 1 u-X 1 + g ; Phillips system) and CN(A 2-X 2 + ; red system). An excitation temperature T exc = 23 000 ± 1900 K and electron densities in the range (0.6-5.6) × 10 16 cm −3 were estimated by means of C + ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C 2 and CN electronically excited species under various laser irradiance conditions are made.
Plasma Sources Science and Technology
We present time- and space-resolved spectroscopic observations of a laser-produced carbon plasma, in an argon background. An Nd : YAG laser pulse, 370 mJ, 3.5 ns, at 1.06 µm, with a fluence of 6.9 J cm−2, is used to produce a plasma from a solid graphite target in a 0.5 to 415 mTorr argon background. The spectral emission in the visible is recorded with 15 ns time resolution. We use 20 ns time resolution plasma imaging, filtered at characteristic carbon species emission wavelengths, to study the dynamics of the expanding plasma. The carbon plasma emission is found to evolve from the characteristic of single ionized carbon, to a more complex one, where C2 and C3 molecular bands dominate. Several plasma fronts, with either ionic or molecular composition, are seen to detach from the laser target plasma. The temporal and spatial features of the molecular carbon species evolution are found to be dependent on the actual argon background pressure.