Spectroscopic evaluation of vibrational temperature and electron density in reduced pressure radio frequency nitrogen plasma

Abstract

The optical emission spectroscopy technique is used to determine the vibrational temperature of the second positive band system,$$ N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ ) in the wavelength range 367.1–380.5 nm by using the line-ratio and Boltzmann plot methods. The electron temperature is evaluated from the intensity ratio of the selected molecular bands corresponding to $$N_{2}^{ + } (B,\upsilon - X, \upsilon^{^{\prime}} , $$ N 2 + ( B , υ - X , υ ′ , 391.44 nm), and, $$N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ , 375.4 nm) transitions, respectively. The selected bands have a different threshold of excitation energies and thus serve as a sensitive indicator of the electron energy distribution function (EEDF). The electron density has been determined from the intensity ratio of the molecular transitions corresponding to $$N_{2}^{ + } (B,\upsilon - X, \upsilon^{^{\prime}} , $$ N 2 + ( B , υ - X , υ ′ , 391.44 nm), and, $$ N_{2} (C,\upsilon^{^{\prime}} - B,\upsilon^{^{\prime\prime}}$$ N 2 ( C , υ ′ - B , υ ″ , 380.5 nm) for different levels of pressure and radio frequency power. The results show that the vibrational temperature decreases with increasing nitrogen fill pressure and radio frequency power. However, the electron temperature increases with radio frequency power and reduces with fill pressure. The electron density increases both with nitrogen fill pressure and radio frequency power that attributes to the effective collisional transfer of energy producing electron impact ionization. Plasma parameters show a significant dependence on discharge conditions and can be fine-tuned for specific surface treatments. Article Highlights Spectrum analysis of RF-driven nitrogen plasma for varying discharge conditions Evaluation of vibrational temperature using line-ratio and Boltzmann plot methods Comparison of vibrational temperatures for line-ratio and Boltzmann plot methods Evaluation of electron temperature and density using the intensity-ratio of bands Correlation of temperature and density with varying fill pressure and RF power

Surface-Active Plasma-Polymerized Nanoparticles for Multifunctional Diagnostic, Targeting, and Therapeutic Probes

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“…The relative intensities and shapes of the emission bands depend on collisional and radiative mechanisms, which create the “spectral fingerprint” for each combination of plasma parameters . Before acetylene inflow, the dominant emission can be attributed to the band emission of the nitrogen ion from the first negative system N 2 + (B 2 ∑ u →X 2 ∑ g ) (0–0).…”

“…The relative intensities and shapes of the emission bands depend on collisional and radiative mechanisms, which create the "spectral fingerprint" for each combination of plasma parameters. 57 Before acetylene inflow, the dominant emission can be attributed to the band emission of the nitrogen ion from the first negative system N 2 + (B 2 ∑ u →X 2 ∑ g ) (0−0). This result is in excellent agreement with the literature and suggests that the dominant direct excitation reaction for this plasma was produced through electron impact ionization 57…”

Water Surface Plasma Source for Large Area Water Treatment by Using Volume Dielectric Barrier Discharge

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“…The primary reason for occurrence of OH is the presence of moisture in SATP air. However, OH emission signals show spectroscopic interference from the N 2 Second Positive system that usually occurs in nitrogen discharges [13]. Recorded spectra in air breakdown dwarf signal strengths that can be measured in combustion processes that utilize oxygen as oxidizer, for example, combustion of hydrocarbons [14,15].…”