C2 Emission Research Articles

Novel superhard BC10N synthesized by microwave plasma CVD

Microwave Plasma Chemical Vapor Deposition (MPCVD) was used to synthesize novel superhard BC10N on silicon substrates. Feedgas mixtures of H2, CH4, N2, and B2H6 were used for a range of systematically varied microwave power, chamber pressure, and flow rate conditions. Optical Emission Spectroscopy (OES) was used to guide the synthesis of BC10N. Plasma optical emission from the C2 peak increases with pressure up to 80 Torr and saturates in the 80–100 Torr range. The C2 emission also follows the same trend, growing non-linearly with increasing microwave power (for fixed chamber pressure of 30 Torr). The presence of abundant C2 in the plasma is advantageous under specific growth conditions to produce superhard carbon-rich BC10N, a material that has been theoretically predicted but not yet synthesized. Findings obtained from X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) elucidate the existence of BC, CN, BN, and B-N-C bonding in the synthesized coating. Nanoindentation hardness measurements are within the superhard regime, showing an average hardness of 63 GPa.

Design and simulation of a utility oilfield flare in Iraq/Kurdistan region using CFD and API-521 methodology

This paper aims at reviewing and analyzing the operation and design of a utility flare in an oilfield in the Iraq/Kurdistan region. The flare supports a gas separation unit that separates 100 MMSCFD of natural gas from other liquid compounds in petroleum refining. The actual flare dimensions are 50 m high and 0.6 m diameter and works in summer where the crosswind speed is 9 m/s and a flow of 1.2 MMSCFD of treated natural gas is flaring through it. At the beginning, the flare design was performed using the API-521 recommended approach based on full operating capacity of the unit and composition of the gas to be flared. The API-521 based design resulted in a flare with a 0.76 m diameter and 48.19 m height. The effects of stack height on heat radiation in case of full capacity firing showed that as the flare height increases from 42.34 m to 133.05 m, the heat radiation decreases from 15.8 kW/m^2 to 1.6 kW/m^2 within 45.7 m dimeter. Furthermore, the relation between stack height and heat radiation was studied for the actual firing rate 1.2MMSCFD using simulation, where the results showed that as the stack height increasing from 10 m to 50 m the heat radiation decreasing from over 1000 w/m^2 to around 150 W/m^2. In fact, CFD code C3d was used to analyze flare performance at normal firing condition during summer operation of 1.2 MMSCFD with a flare diameter and height of 50 m and 0.6 m, respectively. The code was able to predict the flame shape and size during actual flare operation. The results of the simulation demonstrated by defining four locations in the domain to measure the average temperatures and emissions, and to calculate the Combustion Efficiency (CE) and Destruction and Removal Efficiency (DRE). These points were 6 m, 8 m, 10 m, 12 m far from the tip on x-axis and at height of 52 m. The results showed that the average temperature at 6 m far from the flare is 658 K and it decreasing to 490 K at 12 m away from the tip. The CO and CO2 also decreased from 7.27E-5 and 0.033 mass% to 4.53E-6 and 0.027 mass%, respectively. Generally, soot formation was low but at points 8 m and 10 m from the tip the soot formation was considerably lower, respectively at 6.16E-5 and 8.71E-5 mass%. The emissions of C1, C2, C3 and C6+ were measured at 7.46E-9, 5.39E-9, 5.13E-9 and 4.35E-9 mass% at 6 m away from the tip. The emissions increased slightly at 8 m and 10 m from the tip but at 12 m they were observed to decrease. The flare CE and DRE were estimated to be 98% and 100%, respectively. Analysis results confirmed that the flare design was safe and the flare operation was highly efficient with very little smoke produced as indicated by the predicted CE and DRE.

Surface modification of polyethylene using argon and argon/methane DBD atmospheric pressure plasma jet

This article investigates the surface modification of polyethylene (PE) using an atmospheric pressure plasma jet of the DBD type (APPJ) maintained with pure argon (Ar) and with a premixed gas containing 90% argon and 10% of CH4. First and for both plasma jets, the jet length and the optical emissions coming from the plasma species were studied in terms of flow rate and applied voltage. Comparing to Ar, it has been shown that when the premixed gas is used, the jet length gets smaller, the transition point from laminar to turbulent regime was shifted to a low flow rate, and the emission of CH, H2 and C2 appeared, while O and N2 emission coming from ambient air was quenching. The PE surface treatment in both laminar and turbulent regime has been evaluated using water contact angle (WCA) measurement and attenuated total reflection (ATR). The obtained results showed that the hydrophilicity of PE has been improved in both plasma jets due to oxygen group (C=O) incorporation, but Ar plasma jet was observed to induce surface degradation compared to Ar/CH4 plasma due to the higher excited species.

Initial response and combustion behavior of microscale Al/PTFE energetic material by nanosecond laser ignition

Al/PTFE reactive material has potential applications in defense and military due to its good thermodynamic properties and strong stability. To clarify its microscopic reaction process, the initial response and combustion behavior from microsecond up to several milliseconds are fully exhibited via laser-induced plasma spectroscopy and high-speed schlieren photographs while varying the ignition energy. Totally different plasma chemistry and combustion behavior of microscale Al/PTFE (mole ratio of 4:3) from those of pure Al are recorded. The fading of AlO and CN emissions and enhancement of C2 emission from the composite plasma with increase of laser energy prove that Al-F exothermic combination dominate the initial response since the decomposed gases of PTFE keep most Al away from air to be oxidized. The acceleration of laser-induced shockwave by a local high temperature reaction zone at the expanding plume front along the direction of laser beam is illustrated. As the plasma quenched and transformed to combustion at later stage, an ellipsoidal flame generally occurs above the surface for PTFE composite due to the upward move of Al vapor with PTFE decomposition gas while the combustion from pure Al exhibits a horizontal expansion along the surface. Self-sustained combustion of micro-Al/PTFE lasts around 1 ms is observed at extreme high energy of 1100 mJ. Inside flame plume, the transmission of decomposition matter and energy between different flame parts are clarified. Finally, a qualitative reaction model is built to successfully describe the response and combustion behavior after nanosecond laser ignition in detail. This study provides the support for the application of these insensitive reactive materials in laser ignition.

Investigation of the synergetic regulation of O2/Ar preheating treatment and sodium salt addition on semichar combustion characteristics

Using Raman spectroscopy, temperature-programmed desorption (TPD) and laser-induced breakdown spectroscopy (LIBS), the relationship between microstructural characteristics and molecular emissions was determined. It can be concluded that the enhancement of C2 and CN emissions was related to the generation of small aromatic rings and C(O) groups. Compared with the Ar preheating treatment, the presence of additional amount of O2 and sodium salt accelerated the dissociation of the large aromatic ring skeleton, leading to the significant enhancement of small aromatic rings, C(O) and CONa groups. Subsequently, the combustion performance of preheated semichar was investigated by the TG-DTG method. The experimental results demonstrated that pretreatment under oxidizing atmospheres (without and with sodium salt addition) enhanced the comprehensive combustion index (S) and the combustion stability (Rw) of semichars. The corresponding combustion activation energy (E) was weakened. Furthermore, the DFT method was used to analyse the combustion behaviours of semichars. This result demonstrated that preheating treatment (with or without sodium participation) altered the distribution of the Hirshfeld atomic charge (ADCH) of preheated samples, and the combustion essence of semichar was the fracture and recombination of aromatic clusters. For the semichar preheated in the O2/Ar atmosphere, the energy gap of the most optimized pathway was 436.26 kJ/mol. When sodium participated in the oxidizing pretreatment, the energy gap of the most optimized pathway was 413.80 kJ/mol. The positive effect of sodium on the combustion performance of semichar was identified, which was in good agreement with the experimental results.

A novel strategy for preparing calibration standards for laser-induced breakdown spectroscopy using beeswax as a substrate: A case study with cosmetic and lubricant oil samples

A new calibration strategy based on the use of beeswax as a substrate for producing a synthetic multi-elemental calibration standard is proposed for laser-induced breakdown spectroscopy (LIBS). This approach was demonstrated by determining the Fe, Mg, Si, Ti, and Zn in lubricant and cosmetic samples. Besides an external standard calibration, we also proposed calibration strategies with and without the adjustment of mineral oil present in the calibration standards and three other different internal standard calibrations: C I 505.50 nm emission line and C2 516.4 and 545.7 nm emission bands. Concerning the lubricant oil samples, the best results were obtained by using the C2 emission band at 516.4 nm, which was used as an internal standard for determining Si and Zn. The C I emission line at 505.50 nm was the most adequate for Mg quantification, while for Fe quantification, the C2 emission band at 516.4 and 545.7 nm yielded similar results. Regarding the samples of cosmetic products, Si and Ti were quantified adequately by using the C2 emission band at 516.4 nm as an internal standard, while for Mg quantification, better results were achieved by using the C I emission line at 505.50 nm. Finally, for Fe quantification in face foundation and liquid lipstick samples, better results were obtained by employing the C I emission line at 505.50 nm and the C2 emission band at 516.4 nm, respectively. For all elements mentioned above, there was an agreement of between 90 and 110% comparing LIBS with inductively coupled plasma optical emission spectroscopy (ICP OES) and/or inductively coupled plasma mass spectrometry (ICP-MS). All the calibrations curves (using external and internal standards) showed a coefficient of determination (R2) higher than 0.95 and detection limits, in μg g−1, between 4 and 18 for Fe, 4 and 6 for Mg, 8 and 24 for Si, 4 and 14 for Ti, and 4 and 8 for Zn.

Size-dependent melting of onion-like fullerenic carbons: a molecular dynamics and machine learning study

The melting thermodynamic characteristics of 2- to 20-layered onion-like fullerenes (OLF n ) (C60@C240 to C60@···@C6000···@C24000) are comprehensively explored using first-principles-based ReaxFF atomistic simulations and random forest machine learning (RF ML). It is revealed that OLF n shows lower thermal stability than the counterparts of single-walled fullerenes (SWF n ). The melting point of SWF n increases monotonically with increasing size, whereas for OLF n , an unusual size-dependent melting point is observed; OLF n with intermediate size shows the highest melting point. For small OLF n , the melting occurs from the inner to the outer, whereas for large OLF n , it nucleates from the inner to the outer and to intermediate fullerenes. The melting and erosion behaviors of both SWF n and OLF n are mainly characterized by the nucleation of non-hexagons, nanovoids, carbon chains and emission of C2. RF ML model is developed to predict the melting points of both SWF n and OLF n . Moreover, the analysis of the feature importance reveals that the Stone-Wales transformation is a critical pathway in the melting of SWF n and OLF n . This study provides new insights and perspectives into the thermodynamics and pyrolysis chemistry of fullerenic carbons, and also may shed some lights onto the understanding of thermally-induced erosion of carbon-based resources and spacecraft materials.

Investigation of the effect of boron additive to lubricating oil on engine performance, exhaust, and emissions

In this study, the effect of adding doped boron to lubricating oil on engine performance and emissions, in the cases of using gasoline and natural gas as fuel, was investigated in a spark ignition engine. The engine was initially run on a mixture of undoped boron lubricating oil, gasoline, and natural gas. Subsequently, engine performance and emission values were measured in the work, after the engine was run for 50 h. The same measurements were repeated for both the initial values and the values after 50 h with gasoline and natural gas by adding boron to the lubricating oil. Experimental results revealed that using boron-doped lubricating oil causes an average of 2.4–8% reduction in specific fuel consumption when using gasoline and natural gas as fuel in the engine. It was found that the use of boron in the lubricating oil did not make a significant change in C2, CO, and HC emissions, but caused a significant 11.4–12.9% reduction in NOX emissions. As a result, it was observed that adding boron-doped lubricating oil in a gasoline engine provides a relative improvement in engine performance and emissions.

Investigation of the CN and C2 emission characteristics and microstructural evolution of coal to char using laser-induced breakdown spectroscopy and Raman spectroscopy

Laser-induced breakdown spectroscopy (LIBS) was employed to study the spectral characteristics of the C2 and CN emissions of three types of coal and their pyrolysis char samples. By analysing the atomic and molecular emissions, the electron temperature, electron density and rotational temperature were calculated to evaluate the characteristics of the laser-induced plasma. The correlation between the molecular emissions and coal combustion characteristics was also investigated, which was explained from the aspect of microstructural evolution obtained by Raman spectroscopy. The molecular emissions were gradually inhibited with increasing pyrolysis temperatures, however the molecules tended to distribute at a higher equilibrium temperature. The rotational temperatures increase by 1000–3300 K relative to the raw coal for chars prepared at pyrolysis temperatures of 293–1173 K. The reduction of C2 and CN emissions, which are thought to be mainly caused by small aromatic rings and amorphous carbon structures, is consistent with the Raman spectroscopy results in that the microstructures evolve towards a more stable large aromatic-ring skeleton after pyrolysis. When the carbon conversion ratio is Xc = 50% for three kinds of coal, the R2 values of the exponential fitting between C2 emission and carbon conversion rate are all higher than 0.99.

ENIGMATIC NEBULOUS COMPANIONS TO THE GREAT SEPTEMBER COMET OF 1882 AS SOHO-LIKE KREUTZ SUNGRAZERS CAUGHT IN TERMINAL OUTBURST

I investigate the nature of the transient nebulous companions to the sungrazing comet C/1882 R1, known as the Great September Comet. The features were located several degrees to the southwest of the comet's head and reported independently by four observers, including J.F.J. Schmidt and E.E. Barnard, over a period of ten days nearly one month after perihelion, when the comet was 0.7 AU to 1 AU from the Sun. I conclude that none of the nebulous companions was ever sighted more than once and that, contrary to his belief, Schmidt observed unrelated objects on the four consecutive mornings. Each nebulous companion is proposed to have been triggered by a fragment at most a few tens of meters across, released from the comet's nucleus after perihelion and seen only because it happened to be caught in the brief terminal outburst, when its mass was suddenly shattered into a cloud of mostly microscopic debris due possibly to rotational bursting triggered by sublimation torques. The fragment's motion was affected by a strong outgassing-driven nongravitational acceleration with a significant out-of-plane component. Although fragmentation events were common, only a small fraction of nebulous companions was detected because of their transient nature. The observed brightness of the nebulous companions is proposed to have been due mainly to C2 emissions, with a contribution from scattering of sunlight by the microscopic dust. By their nature, the fragments responsible for the nebulous companions bear a strong resemblance to the dwarf Kreutz sungrazers detected with the coronagraphs aboard the SOHO space probe. Only their fragmentation histories are different and the latter display no terminal outburst, a consequence of extremely short lifetimes of the sublimating icy and refractory material in the Sun's corona.

Photometry and long-slit spectroscopy of the split comet C/2019 Y4 (ATLAS)

ABSTRACT We present an analysis of the photometric and spectroscopic observations of the split comet C/2019 Y4 (ATLAS). Observations were carried out on 2020 April 14 and 16, when the heliocentric distance of the comet was 1.212 and 1.174 au, its geocentric distance 0.998 and 0.991 au, and the phase angle 52.°9 and 54.°5, respectively. The comet was observed with the 6-m BTA (Big Telescope Alt-azimuth) telescope of the Special Astrophysical Observatory (Russia) with the SCORPIO-2 (Spectral Camera with Optical Reducer for Photometric and Interferometric Observations) multimode focal reducer. The narrow-band BC and RC cometary filters in the continuum were used. We identified numerous emissions of CN, C2, C3, and NH2 molecules within the range of 3750–7100 Å. The C2/CN and C3/CN production rate ratios coincide with those of typical comets. Four fragments belonging to the coma were detected in both observational runs. We compared and analysed temporal variations of the visual magnitudes, gas productivity, and dust colour. Based on our dynamical investigation of the orbits of comets C/1844 Y1 (Great comet) and C/2019 Y4 (ATLAS), we can claim that, with high probability, the two comets do not have a common progenitor.

Laser-Induced Breakdown Spectroscopy (LIBS) For The Characterization Of Methane-Air Laminar Diffusion Flame

Laser-induced breakdown spectroscopy (LIBS) was applied for the characterization of the methane-air laminar diffusion flame, revealing the spatial distribution of its composition. From the measurement, it was found that distribution of the atomic and ionic N emissions produced by the flame had obvious differences, which were mainly distributed in the air area and flame area, respectively. A comparison of the LIBS spectra of air, methane gas, and methane-air laminar diffusion flame showed that the atomic N emissions were mainly produced by the excitation of N2, and the ionic N emissions were more related to the N-containing combustion products. In addition, the correlation between typical emissions and the flame temperature measured by thermocouple was estimated to show that the tendency of the changes in temperature can be characterized by C2 emission intensities. This work provides a new method for real-time online flame temperature measurement, and also provides a reference for revealing the formation process and conversion pathway of each component in the flame.

Laser-Induced Breakdown Spectroscopy Combined with Temporal Plasma Analysis of C2 Molecular Emission for Carbon Analysis in Coal

A benchtop laser-induced breakdown spectroscopy is demonstrated to determine the elemental carbon content present in raw coal used for combustion in power plants. The spectral intensities of molecular CN and C2 emission are measured together with the atomic carbon (C) and other inorganic elements (Si, Fe, Mg, Al, Ca, Na, and K) in the laser-induced breakdown spectroscopy spectrum of coal. The emission persistence time of C2 molecule emission is measured from the coal plasma generated by a nanosecond laser ablation with a wavelength of 266 nm in the Ar atmosphere. The emission persistence time of molecular C2 emission along with the spectral intensities of major ash elements (Fe, Si, Al, and Ca) and carbon emissions (atomic C, molecular CN, and C2) shows a better relationship with the carbon wt% of different coal samples. The calibration model to measure elemental carbon (wt%) is developed by combining the spectral characteristics (spectral intensity) and the temporal characteristics (emission persistence time of C2 molecule emission). The temporal characteristic studies combined with the spectroscopic data in the partial least square regression model have resulted in an improvement in the root mean square error of validation, and the relative standard deviation is reduced from 10.8% to 4.1% and from 11.3% to 6.0%, respectively.

Imaging and Modeling C2 Radical Emissions from Microwave Plasma-Activated Methane/Hydrogen Gas Mixtures: Contributions from Chemiluminescent Reactions and Investigations of Higher-Pressure Effects and Plasma Constriction.

Wavelength and spatially resolved imaging and 2D plasma chemical modeling methods have been used to study the emission from electronically excited C2 radicals in microwave-activated dilute methane/hydrogen gas mixtures under processing conditions relevant to the chemical vapor deposition (CVD) of diamond. Obvious differences in the spatial distributions of the much-studied C2(d3Πg-a3Πu) Swan band emission and the little-studied, higher-energy C2(C1Πg-A1Πu) emission are rationalized by invoking a chemiluminescent (CL) reactive source, most probably involving collisions between H atoms and C2H radicals, that acts in tandem with the widely recognized electron impact excitation source term. The CL source is relatively much more important for forming C2(d) state radicals and is deduced to account for >40% of C2(d) production in the hot plasma core under base operating conditions, which should encourage caution when estimating electron or gas temperatures from C2 Swan band emission measurements. Studies at higher pressures (p ≈ 400 Torr) offer new insights into the plasma constriction that hampers efforts to achieve higher diamond CVD rates by using higher processing pressures. Plasma constriction is proposed as being inevitable in regions where the local electron density (ne) exceeds some critical value (nec) and electron-electron collisions enhance the rates of H2 dissociation, H-atom excitation, and related associative ionization processes relative to those prevailing in the neighboring nonconstricted plasma region. The 2D modeling identifies a further challenge to high-p operation. The radial uniformities of the CH3 radical and H-atom concentrations above the growing diamond surface both decline with increasing p, which are likely to manifest as less spatially uniform diamond growth (in terms of both rate and quality).

Identification and analysis of factors influencing climate change in terms of CO2 emissions

It is commonly known that transport means release exhaust gases into the atmosphere which poses a threat to the natural environment. Therefore, new requirements and stricter regulations on emissions of C2 and other harmful substances are being introduced. This study presents an analysis of different emission sources of anthropogenic and natural origin. The analysis is supposed to show a real impact of transport related C2 emissions on the natural environment. The work includes results of tests concerning application of biocomponents in motor vehicle fuels and their impact on the value of C2 emission. Having in mind the analysis, it can be said that, as compared to other branches of economy and its natural sources, transport is not the major source of C2 emission and application of biofuels is not a factor that is likely to significantly contribute to carbon dioxide emission reduction on a global scale.

Optical diagnostics of microwave plasma in process of micro/nanocrystalline diamond deposition on hard alloy tools

Diamond coatings on hard alloy tools produced by chemical vapor deposition (CVD) from methane-hydrogen mixtures greatly enhance the functional properties such as wear resistance and quality of the material processing. By varying the gas composition during the diamond film growth it is possible to cyclically change the film structure between microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) to produce MCD/NCD multilayers that improves the mechanical properties of the film and reduces its stress and roughness. As the diamond growth occurs with participation of radicals generated in the plasma thermo-chemical reactions it is important to control in situ the presence of those species and gas temperature Tg. Here we used optical emission spectroscopy (OES) to monitor atomic hydrogen, CN, CH and C2 dimer radicals in course of deposition of MCD/NCD coatings by microwave plasma CVD in CH4-H2 and CH4-N2-H2 mixtures. The gas temperature has been calculated from analysis of rotational components of structure of C2(Δν = 0) emission line. We found that addition of nitrogen (4%) in CH4-H2 plasma, which is needed to form NCD, significantly, by about 500 K reduces Tg (from Tg = 3910 K to Tg = 3330 K). We developed an algorithm tolerable to small shifts of the measured spectral lines which provided fast calculation of Tg, so that the spectrum record and the automatic processing of fine structure of C2(Δν = 0) line totally take the time of about 5 min.

Analysis of Nonmetallic Constituents of Lubricating Oil Using Indirect Ablation Laser-Induced Breakdown Spectroscopy

Indirect ablation laser-induced breakdown spectroscopy (IA-LIBS) was applied to the analysis of the nonmetallic constituents of engine oil and considered as a feasible technique for the evaluation of the consumption and/or combustion of engine oil during routine engine operation. The evolution of CN emission and C2 emission was investigated for different driving time intervals of the motor. The exponentially decaying curve showed that the intensity of CN emission and C2 emission decayed at different driving time intervals. The evolution of total CN emission and C2 emission was analyzed, and the ratio of CN to C2 was calculated, which might be taken as an indicator to evaluate the performance of the used engine oils and/or to diagnose the conditions of the motor engine. Thus, it is shown that IA-LIBS is a potential method for analyzing the metallic and nonmetallic constituents of engine oil.

Diamond chemical vapor deposition using a zero-total gas flow environment

We demonstrate diamond growth through microwave plasma-enhanced chemical vapor deposition using a sealed (static-mode) CH4/H2 process gas mixture. The growth experiments were complemented by spatially and spectrally resolved optical emission imaging measurements of electronically excited C2 and CH radicals in the hot plasma core. The as-grown material was characterized by Raman Spectroscopy and Scanning Electron Microscopy and shown to be typical of polycrystalline diamond grown using traditional methods. Moreover, this material was essentially indistinguishable from material grown using a tracked flow-mode of operation in which the input methane flow rate was progressively reduced to mimic the time evolving C2 emission intensities in the static-mode experiments. These proving static-mode studies demonstrate a ~30-fold improvement (cf. that achieved using standard flow-mode conditions) in the conversion efficiency of carbon in the input source gas into diamond, and we argue that further gains should be possible with appropriate reactor and process optimization. Static-flow growth could be particularly advantageous in the case of depositions using limited, expensive, hazardous, or environmentally damaging feedstock gases.

Comparative study among waste cooking oil blends flame spectroscopy as an alternative fuel through using an industrial burner

The presented experimental investigation aims at providing a microscopic insight into the flame characteristics of the conventional (light/heavy diesel), a renewable fuel (waste cooking oil), and its blends with light/heavy diesel oils. A hyperspectral camera is used to provide detailed information on fuel reactivity and radiation intensities within the flame zones via the analysis of the C2 and CH radiation emissions. The experiments cover four equivalence ratios (Φ) of 0.63, 0.75, 0.96, and 1.1. A coaxial disc stabilized burner having a twin air jet atomizer is employed. The flame images are taken in the open atmosphere and the assessment of the combustion efficiency is obtained through the measurements of the cooling load inside a cylindrical combustor. The calculated values of the spatial cross-sectional average flame temperatures along the different flames are compared with the corresponding values obtained by a type S thermocouple. The processing of the hyperspectral flame images proves to be an extremely useful tool to define the location, size, and characteristics of the flame zones. The burning of HDO/WCO blend at near stoichiometric conditions appears to be a viable renewable alternative to burning standalone HDO. The burning of a standalone waste cooking oil must be avoided.

Plasma chemistry produced during laser ablation of graphite in air, argon, helium and nitrogen

Laser-induced plasma chemistry produced during the ablation of graphite targets at atmospheric pressure in air, argon, helium and nitrogen was studied through time-resolved atomic and molecular emission spectroscopy. The plasma plume and plasma chemistry were generated by focusing a 6-mm diameter, 212 mJ, 1064-nm nanosecond Nd:YAG laser to a spot size of about 1 mm diameter over graphite samples of 99.9% pureness. The atomic emissions C I 247.86 nm, N I 821.50 nm and O I 777.19 nm, and the molecular bands C2 (473.71 nm) and CN (359.04 nm and 388.30 nm) were monitored as a function of time (0.2 to 220 μs). While the C I and C2 emissions followed a near-exponential decay, the CN emission in air and nitrogen showed an emission behavior characterized by two local maxima at 0.2 μs and 20–30 μs after the plasma ignition. The first maximum was explained by the early plasma chemistry produced by the ablated carbon species and the confining background gas, whereas the second maximum was attributed to atomic recombination and shock wave-induced excitation of the plasma plume. Two main effects were observed when the ablation was produced in different background gases. First, the presence of oxygen (≈21%) in air had a negligible effect on atomic lines; however, the CN emission intensity and lifetime were significantly reduced in comparison with an atmosphere of 100% nitrogen. This was attributed to the reduction of nitrogen species as reaction partners during the plasma chemistry in air. Secondly, due to the assumed higher plasma temperature in Ar, this gas favored the emission intensity and lifetime of atomic species but hindered the formation of C2 species. Because the collection optics of the emission spectroscopy system was configured in backscatter mode, which integrates over the entire plasma volume and gate time without spatial resolution, the time-resolved behavior of the plasma emissions were only related to the number density of emitters but not to specific locations in the plasma volume.