Nitrogen and Nitrogen-Hydrogen plasma emission spectrum in the 800-2000 nm range. Different atomic transitions are distinguished by rectangles (300W, 0.1 Torr, 10 sccm). 

Contexts in source publication

Context 1

... controllers. The remote plasma column was created in N 2 and N 2 +H 2 gas at pressures ranging from 0.5 to 3 Torr. The microwave (2.45 GHz) power delivered to the resonnance cavity was 300 W. As aforementioned, the plasma characterisation was performed using IR emission spectroscopy. The near infrared spectra were recorded with a FTLA2000 FTIR (770-300 nm) spectrometer purchased from ABB-Bomem (Québec, QC, Canada) at a resolution of 2 cm -1 . For infrared collection, the IR light exiting through a ZnSe feedthrough window, was expanded through a concave ZnSe lens then was redirected by a concave gold mirror into the FTIR’s entrance port. The detector used during each experiment was a thermoelectrically cooled Indium Arsenide (InAs) semiconductor diode which is sensitive in the range of 3000-14000 cm -1 (710-3300 nm). One hundred interferograms were routinely co-added and Fourier- transformed, thereby enabling to record spectra with an acceptable signal-to-noise ratio and reasonable acquisition time. Typical infrared emission spectrum of the N 2 and N 2 +H 2 microwave discharge is shown in Fig. 2 . In the present study, the observed infrared N 2 spectra consisted mostly of N 2 first positive transitions. In addition, spectra recorded at low gas pressures p ≤ 1 Torr allow visualizing various N I atomic transitions. In the illustrated spectrum, the infrared features are related to different vibrational transitions originating from the first positive system of nitrogen N 2 ( B 3 ∏ g → A 3 ∑ u + ) . Moreover, as shown in Fig. 2 , the N 2 +H 2 plasma consisted mainly of N 2 first positive transitions. Also of interest, emission spectroscopy in the IR region allows detecting nitrogen atomic transitions. Indeed, no intense atomic transition in the UV- Visible spectral region is detectable in the pressure and microwave power ranges selected for this study. However, atomic emission lines can be easily observed in the near-infrared. The most intense lines are highlighted by rectangles in Fig. 2 . One of them located at 939.3, is assigned to 2 P- 2 D o transitions. Other strong lines are observed at 1359 nm and 1343 nm and are due to [[ 2 P- 2 S 0 (or 2 D 0 - 2 P)]] and 2 P - 2 S° atomic transitions, respectively. In N 2 +H 2 plasmas, an intense hydrogen atomic transition is detectable at 1875 nm which is due to [4-3, Paschen α ] transition while that observed at 1282 nm is assigned to [5-4 Paschen β ] transition. Figure 3 shows the pressure dependence of the aforementioned atomic transitions. These results indicate that the concentration of excited nitrogen and hydrogen atoms decreased with increasing gas pressure, coming in part from a decrease of electron temperature [2] and thus of electron excitation rate of atoms with gas pressure. Moreover, by increasing the pressure, ions undergo more frequent collisions. Therefore the ions do not acquire enough energy to dissociate the molecules during collisions. The relative intensity of the N 2 rotational transitions measured in the spectra are generally described by a Boltzmann distribution, with the rotational temperature determined from these transitions being close to the gas temperature [3]. In principle, the rotational temperature of N 2 can be determined either by using different bands from the first negative or the second positive systems [4] through a Boltzmann plot, provided that the spectrometer resolution is high enough to separate the rotational structure of the bands, or by fitting numerical models to the band envelope when medium to low resolution spectrometers are used. However, despite the intrinsisic characteristics of the 1 st positive system that make it a more reliable tool for gas temperature estimation (low excitation threshold, long radiative lifetimes, higher predissociation level, and high emission intensity) its complex structure with 27 rotational branches has hampered the widespread use of it for gas temperature determination [3, 5]. Inspired by Biloiu et al . [3] the plasma gas temperature was evaluated by calculating and generating theoretical spectra closely matching the bands originating from 0-0 transition in the N 2 1 st positive system which is observed in the range of 1025-1055 nm. To that end, a synthetic spectrum which was automated in MATLAB TM [3] has been used. However, such a procedure requires the knowledge of the FTIR spectrometer response function which, in turn, has to be convolved with the calculated spectrum. Accordingly, the shape parameters of the 826 nm ArI line taken from the spectrum of an ArHg source was used, considering that the instrumental broadening could be modeled by a pseudo-Voigt function: where p and 1 − p are the relative magnitudes of the Gaussian and Lorentzian functions contributions, respectively, w is the full width at half maximum of the selected Ar line (FWHM), and λ 0 is the central wavelength. This allowed determining that p value was 0.5 while w was 0.2 nm for the experimental setup used in the present study. It is worth mentioning that the p value has an error of ± 0.1. However, this has minimal effect on the temperature calculation as can be seen from the error bars on the curves presented in Fig. 5 . Figure 4 shows an example of a measured ro- vibrational N 2 spectrum along with the corresponding spectrum calculated using the aforementioned protocol. As can be seen, an excellent match between the calculated and experimental spectra was obtained, with a confidence level better than 95%. This method was thereafter used to characterize the pressure-dependence of the rotational temperature in N 2 and N 2 +H 2 plasmas generated at powers of 300 W. As seen in Fig. 5 , T r increased with pressure and power due to the more frequent collisions occurring between the plasma species which lead to a decrease in electron temperature and ion temperature with concomitant increase of gas temperature. The present results clearly highlighted that emission spectroscopy in the near IR region provides different information compared to UV-Visible emission spectroscopy. As an example, the numerical simulation of the spectrum of the 0-0 transition of the nitrogen first positive system allows calculating rotational temperatures [2]. Optical emission spectroscopy in the near IR spectral region was used for the diagnostic of low pressure N 2 and N 2 +H 2 microwave discharges currently used for modifying the surface of biomedical polymers. The experimental infrared spectra consisted mostly of N 2 1 st positive system transitions and N and H atomic transitions. Rotational temperatures were accurately measured by fitting the N 2 1 st positive system spectra recorded from plasmas generated at 0.5 to 3 Torr of N 2 and N 2 +H 2 with powers of 300 W. Under these conditions, the N 2 +H 2 rotational temperatures increased as compared to N 2 rotational temperature in similar pressure ...

Context 2

... controllers. The remote plasma column was created in N 2 and N 2 +H 2 gas at pressures ranging from 0.5 to 3 Torr. The microwave (2.45 GHz) power delivered to the resonnance cavity was 300 W. As aforementioned, the plasma characterisation was performed using IR emission spectroscopy. The near infrared spectra were recorded with a FTLA2000 FTIR (770-300 nm) spectrometer purchased from ABB-Bomem (Québec, QC, Canada) at a resolution of 2 cm -1 . For infrared collection, the IR light exiting through a ZnSe feedthrough window, was expanded through a concave ZnSe lens then was redirected by a concave gold mirror into the FTIR’s entrance port. The detector used during each experiment was a thermoelectrically cooled Indium Arsenide (InAs) semiconductor diode which is sensitive in the range of 3000-14000 cm -1 (710-3300 nm). One hundred interferograms were routinely co-added and Fourier- transformed, thereby enabling to record spectra with an acceptable signal-to-noise ratio and reasonable acquisition time. Typical infrared emission spectrum of the N 2 and N 2 +H 2 microwave discharge is shown in Fig. 2 . In the present study, the observed infrared N 2 spectra consisted mostly of N 2 first positive transitions. In addition, spectra recorded at low gas pressures p ≤ 1 Torr allow visualizing various N I atomic transitions. In the illustrated spectrum, the infrared features are related to different vibrational transitions originating from the first positive system of nitrogen N 2 ( B 3 ∏ g → A 3 ∑ u + ) . Moreover, as shown in Fig. 2 , the N 2 +H 2 plasma consisted mainly of N 2 first positive transitions. Also of interest, emission spectroscopy in the IR region allows detecting nitrogen atomic transitions. Indeed, no intense atomic transition in the UV- Visible spectral region is detectable in the pressure and microwave power ranges selected for this study. However, atomic emission lines can be easily observed in the near-infrared. The most intense lines are highlighted by rectangles in Fig. 2 . One of them located at 939.3, is assigned to 2 P- 2 D o transitions. Other strong lines are observed at 1359 nm and 1343 nm and are due to [[ 2 P- 2 S 0 (or 2 D 0 - 2 P)]] and 2 P - 2 S° atomic transitions, respectively. In N 2 +H 2 plasmas, an intense hydrogen atomic transition is detectable at 1875 nm which is due to [4-3, Paschen α ] transition while that observed at 1282 nm is assigned to [5-4 Paschen β ] transition. Figure 3 shows the pressure dependence of the aforementioned atomic transitions. These results indicate that the concentration of excited nitrogen and hydrogen atoms decreased with increasing gas pressure, coming in part from a decrease of electron temperature [2] and thus of electron excitation rate of atoms with gas pressure. Moreover, by increasing the pressure, ions undergo more frequent collisions. Therefore the ions do not acquire enough energy to dissociate the molecules during collisions. The relative intensity of the N 2 rotational transitions measured in the spectra are generally described by a Boltzmann distribution, with the rotational temperature determined from these transitions being close to the gas temperature [3]. In principle, the rotational temperature of N 2 can be determined either by using different bands from the first negative or the second positive systems [4] through a Boltzmann plot, provided that the spectrometer resolution is high enough to separate the rotational structure of the bands, or by fitting numerical models to the band envelope when medium to low resolution spectrometers are used. However, despite the intrinsisic characteristics of the 1 st positive system that make it a more reliable tool for gas temperature estimation (low excitation threshold, long radiative lifetimes, higher predissociation level, and high emission intensity) its complex structure with 27 rotational branches has hampered the widespread use of it for gas temperature determination [3, 5]. Inspired by Biloiu et al . [3] the plasma gas temperature was evaluated by calculating and generating theoretical spectra closely matching the bands originating from 0-0 transition in the N 2 1 st positive system which is observed in the range of 1025-1055 nm. To that end, a synthetic spectrum which was automated in MATLAB TM [3] has been used. However, such a procedure requires the knowledge of the FTIR spectrometer response function which, in turn, has to be convolved with the calculated spectrum. Accordingly, the shape parameters of the 826 nm ArI line taken from the spectrum of an ArHg source was used, considering that the instrumental broadening could be modeled by a pseudo-Voigt function: where p and 1 − p are the relative magnitudes of the Gaussian and Lorentzian functions contributions, respectively, w is the full width at half maximum of the selected Ar line (FWHM), and λ 0 is the central wavelength. This allowed determining that p value was 0.5 while w was 0.2 nm for the experimental setup used in the present study. It is worth mentioning that the p value has an error of ± 0.1. However, this has minimal effect on the temperature calculation as can be seen from the error bars on the curves presented in Fig. 5 . Figure 4 shows an example of a measured ro- vibrational N 2 spectrum along with the corresponding spectrum calculated using the aforementioned protocol. As can be seen, an excellent match between the calculated and experimental spectra was obtained, with a confidence level better than 95%. This method was thereafter used to characterize the pressure-dependence of the rotational temperature in N 2 and N 2 +H 2 plasmas generated at powers of 300 W. As seen in Fig. 5 , T r increased with pressure and power due to the more frequent collisions occurring between the plasma species which lead to a decrease in electron temperature and ion temperature with concomitant increase of gas temperature. The present results clearly highlighted that emission spectroscopy in the near IR region provides different information compared to UV-Visible emission spectroscopy. As an example, the numerical simulation of the spectrum of the 0-0 transition of the nitrogen first positive system allows calculating rotational temperatures [2]. Optical emission spectroscopy in the near IR spectral region was used for the diagnostic of low pressure N 2 and N 2 +H 2 microwave discharges currently used for modifying the surface of biomedical polymers. The experimental infrared spectra consisted mostly of N 2 1 st positive system transitions and N and H atomic transitions. Rotational temperatures were accurately measured by fitting the N 2 1 st positive system spectra recorded from plasmas generated at 0.5 to 3 Torr of N 2 and N 2 +H 2 with powers of 300 W. Under these conditions, the N 2 +H 2 rotational temperatures increased as compared to N 2 rotational temperature in similar pressure ...

Context 3

... controllers. The remote plasma column was created in N 2 and N 2 +H 2 gas at pressures ranging from 0.5 to 3 Torr. The microwave (2.45 GHz) power delivered to the resonnance cavity was 300 W. As aforementioned, the plasma characterisation was performed using IR emission spectroscopy. The near infrared spectra were recorded with a FTLA2000 FTIR (770-300 nm) spectrometer purchased from ABB-Bomem (Québec, QC, Canada) at a resolution of 2 cm -1 . For infrared collection, the IR light exiting through a ZnSe feedthrough window, was expanded through a concave ZnSe lens then was redirected by a concave gold mirror into the FTIR’s entrance port. The detector used during each experiment was a thermoelectrically cooled Indium Arsenide (InAs) semiconductor diode which is sensitive in the range of 3000-14000 cm -1 (710-3300 nm). One hundred interferograms were routinely co-added and Fourier- transformed, thereby enabling to record spectra with an acceptable signal-to-noise ratio and reasonable acquisition time. Typical infrared emission spectrum of the N 2 and N 2 +H 2 microwave discharge is shown in Fig. 2 . In the present study, the observed infrared N 2 spectra consisted mostly of N 2 first positive transitions. In addition, spectra recorded at low gas pressures p ≤ 1 Torr allow visualizing various N I atomic transitions. In the illustrated spectrum, the infrared features are related to different vibrational transitions originating from the first positive system of nitrogen N 2 ( B 3 ∏ g → A 3 ∑ u + ) . Moreover, as shown in Fig. 2 , the N 2 +H 2 plasma consisted mainly of N 2 first positive transitions. Also of interest, emission spectroscopy in the IR region allows detecting nitrogen atomic transitions. Indeed, no intense atomic transition in the UV- Visible spectral region is detectable in the pressure and microwave power ranges selected for this study. However, atomic emission lines can be easily observed in the near-infrared. The most intense lines are highlighted by rectangles in Fig. 2 . One of them located at 939.3, is assigned to 2 P- 2 D o transitions. Other strong lines are observed at 1359 nm and 1343 nm and are due to [[ 2 P- 2 S 0 (or 2 D 0 - 2 P)]] and 2 P - 2 S° atomic transitions, respectively. In N 2 +H 2 plasmas, an intense hydrogen atomic transition is detectable at 1875 nm which is due to [4-3, Paschen α ] transition while that observed at 1282 nm is assigned to [5-4 Paschen β ] transition. Figure 3 shows the pressure dependence of the aforementioned atomic transitions. These results indicate that the concentration of excited nitrogen and hydrogen atoms decreased with increasing gas pressure, coming in part from a decrease of electron temperature [2] and thus of electron excitation rate of atoms with gas pressure. Moreover, by increasing the pressure, ions undergo more frequent collisions. Therefore the ions do not acquire enough energy to dissociate the molecules during collisions. The relative intensity of the N 2 rotational transitions measured in the spectra are generally described by a Boltzmann distribution, with the rotational temperature determined from these transitions being close to the gas temperature [3]. In principle, the rotational temperature of N 2 can be determined either by using different bands from the first negative or the second positive systems [4] through a Boltzmann plot, provided that the spectrometer resolution is high enough to separate the rotational structure of the bands, or by fitting numerical models to the band envelope when medium to low resolution spectrometers are used. However, despite the intrinsisic characteristics of the 1 st positive system that make it a more reliable tool for gas temperature estimation (low excitation threshold, long radiative lifetimes, higher predissociation level, and high emission intensity) its complex structure with 27 rotational branches has hampered the widespread use of it for gas temperature determination [3, 5]. Inspired by Biloiu et al . [3] the plasma gas temperature was evaluated by calculating and generating theoretical spectra closely matching the bands originating from 0-0 transition in the N 2 1 st positive system which is observed in the range of 1025-1055 nm. To that end, a synthetic spectrum which was automated in MATLAB TM [3] has been used. However, such a procedure requires the knowledge of the FTIR spectrometer response function which, in turn, has to be convolved with the calculated spectrum. Accordingly, the shape parameters of the 826 nm ArI line taken from the spectrum of an ArHg source was used, considering that the instrumental broadening could be modeled by a pseudo-Voigt function: where p and 1 − p are the relative magnitudes of the Gaussian and Lorentzian functions contributions, respectively, w is the full width at half maximum of the selected Ar line (FWHM), and λ 0 is the central wavelength. This allowed determining that p value was 0.5 while w was 0.2 nm for the experimental setup used in the present study. It is worth mentioning that the p value has an error of ± 0.1. However, this has minimal effect on the temperature calculation as can be seen from the error bars on the curves presented in Fig. 5 . Figure 4 shows an example of a measured ro- vibrational N 2 spectrum along with the corresponding spectrum calculated using the aforementioned protocol. As can be seen, an excellent match between the calculated and experimental spectra was obtained, with a confidence level better than 95%. This method was thereafter used to characterize the pressure-dependence of the rotational temperature in N 2 and N 2 +H 2 plasmas generated at powers of 300 W. As seen in Fig. 5 , T r increased with pressure and power due to the more frequent collisions occurring between the plasma species which lead to a decrease in electron temperature and ion temperature with concomitant increase of gas temperature. The present results clearly highlighted that emission spectroscopy in the near IR region provides different information compared to UV-Visible emission spectroscopy. As an example, the numerical simulation of the spectrum of the 0-0 transition of the nitrogen first positive system allows calculating rotational temperatures [2]. Optical emission spectroscopy in the near IR spectral region was used for the diagnostic of low pressure N 2 and N 2 +H 2 microwave discharges currently used for modifying the surface of biomedical polymers. The experimental infrared spectra consisted mostly of N 2 1 st positive system transitions and N and H atomic transitions. Rotational temperatures were accurately measured by fitting the N 2 1 st positive system spectra recorded from plasmas generated at 0.5 to 3 Torr of N 2 and N 2 +H 2 with powers of 300 W. Under these conditions, the N 2 +H 2 rotational temperatures increased as compared to N 2 rotational temperature in similar pressure ...