Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • A novel state-resolved actinometry method to determine the nitrogen atom number density in the ground state and intra-shell excited states in low-pressure electron cyclotron resonance plasmas
Title: A novel state-resolved actinometry method to determine the nitrogen atom number density in the ground state and intra-shell excited states in low-pressure electron cyclotron resonance plasmas
Abstract The active-particle number density is a key parameter for plasma material processing, space propulsion, and plasma-assisted combustion. The traditional actinometry method focuses on measuring the density of the atoms in the ground state, but there is a lack of an effective optical emission spectroscopy method to measure intra-shell excited-state densities. The latter atoms have chemical selectivity and higher energy, and they can easily change the material morphology as well as the ionization and combustion paths. In this work, we present a novel state-resolved actinometry (SRA) method, supported by a krypton line-ratio method for the electron temperature and density, to measure the number densities of nitrogen atoms in the ground and intra-shell excited states. The SRA method is based on a collisional-radiative model, considering the kinetics of atomic nitrogen and krypton including their excited states. The densities measured by our method are compared with those obtained from a dissociative model in a miniature electron cyclotron resonance (ECR) plasma source. Furthermore, the saturation effect, in which the electron density remains constant due to the microwave propagation in an ECR plasma once the power reaches a certain value, is used to verify the electron density measured by the line-ratio method. An ionization balance model is also presented to examine the measured electron temperature. All the values obtained with the different methods are in good agreement with each other, and hence a set of verified rate coefficient data used in our method can be provided. A novel concept, the ‘excited-state system’, is presented to quickly build an optical diagnostic method based on the analysis of quantum number propensity and selection rules.  more » « less
Award ID(s):
2110023
PAR ID:
10511446
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Institute of Physics
Date Published:
Journal Name:
Plasma Sources Science and Technology
Volume:
33
Issue:
5
ISSN:
0963-0252
Page Range / eLocation ID:
055006
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Spectrochimica Acta Part B: Atomic Spectroscopy)
    Metal plasma has been widely applied in hard coatings or metallization of vias and trenches in semiconductor device fabrication. Ion irradiation plays a vital role in the film properties. Previous methods have focused on the Ti atom and Ti+ ion number densities; however, there is a lack of a practical optical emission spectroscopy method for measuring the Ti2+ ion number density. High-charge-state ions lead to high compressive stress, especially in high-power impulse magnetron sputtering (HiPIMS) and vacuum arc plasma devices with a high ionization fraction. In this work, we present a novel charge-state resolved OES method to obtain the time-resolved Ti+ and Ti2+ ion number densities. This method is based on the excited-state cycle mechanisms of Ti+(4p) and Ti2+(4p) emitting states, as determined by kinetic investigations using a collisional-radiative model. In the excited-state cycle mechanisms, the Ti+/Ti2+ line-ratio is found to be sensitive to the ion ratio, and the Ti2+ line-ratio is sensitive to the electron density. The latter can decouple the influence of the electron density on the Ti+/Ti2+ line ratio, allowing the Ti+ and Ti2+ ion number densities to be determined by combining the above line ratios. This method is verified in a vacuum arc titanium metal plasma source. 
    more » « less
  2. ; (, American Institute of Aeronautics and Astronautics)
    This contribution presents a state-to-state model of femtosecond plasma filamentgenerated in atmospheric pressure air. Previous experimental studies using opticalemission spectroscopy have shown that the short-lived early emission is dominated by theN 2(C-B) and N 2+ (B-X) transitions. Surprisingly, N 2(C-B) emission is observed only withinthe first 6 ns after the pulse, while N 2+ (B-X) is limited to the first 2 ns. The main goal ofthis study is to develop a detailed state-to-state plasma kinetic model that can provide abetter understanding of the main pathways leading to the formation and destruction ofthese excited nitrogen species. It was found numerically that N 2(C) is primarily formed viathe dissociative recombination of the intermediate N4+ ion. In contrast, the N 2+ (B) comesprimarily from the electron impact excitation reaction with N2+ (X), which is generatedduring the fs ionization process. The model’s predictions of species lifetimes show goodagreement with experimental measurements. These results are important for improvingthe understanding of early-time emission from femtosecond filaments, with implicationsfor applications such as femtosecond laser-induced breakdown spectroscopy (fs-LIBS),pre-ionization schemes, directed energy systems, or plasma-assisted combustion. 
    more » « less
  3. ; ; ; (, Plasma Sources Science and Technology)
    Abstract Nano-second, capillary discharges (nCDs) are unique plasma sources in their ability to sustain high specific energy deposition ω dep approaching 10 eV/molecule in molecular gases. This high energy loading on short timescales produces both high plasma densities and high densities of molecular exited states. These high densities of electrons and excited states interact with each other during the early afterglow through electron collision quenching and associative ionization. In this paper we discuss results from a two-dimensional computational investigation of a nCD sustained in air at a pressure of 28.5 mbar and with a voltage amplitude 20 kV. Discharges were investigated for two circuit configurations—a floating low voltage electrode and with the low voltage electrode connected to ground through a ballast resistor. The first configuration produced a single ionization wave from the high to low voltage electrode. The second produced converging ionization waves beginning at both electrodes. With a decrease of the tube radius, the velocity of the ionization fronts decreased while the shape of the ionization wave changed from the electron density being distributed smoothly in the radial direction, to being hollow shaped where there is a higher electron density near the tube wall. For sufficiently small tubes, the near-wall maxima merge to have the higher density on the axis of the capillary tube. In the early afterglow, the temporal and radial behavior of the N 2 (C 3 Π u ) density is a sensitive function of ω dep due to electron collision quenching. These trends indicate that starting from ω dep ⩾ 0.3 eV/molecule, it is necessary to take into account interactions of electrons with electronically excited species during the discharge and early afterglow. 
    more » « less
  4. ; ; ; ; ; (, Astronomy & Astrophysics)
    Context.Quasar outflows play a significant role in the active galactic nucleus (AGN) feedback, impacting the interstellar medium and potentially influencing galaxy evolution. Characterizing these outflows is essential for understanding AGN-driven processes. Aims.We aim to analyze the physical properties of the mini-broad absorption line outflow in quasar J1402+2330 using data from the Dark Energy Spectroscopic Instrument (DESI) survey. We seek to measure the outflow’s location, energetics, and potential impact on AGN feedback processes. Methods.In the spectrum of J1402+2330, we identify multiple ionic absorption lines, including ground and excited states. We measure the ionic column densities and then use photoionization models to determine the total hydrogen column density and ionization parameter of the outflow. We utilized the population ratio of the excited state to the ground state of N IIIand S IVto determine the electron number density. Results.The derived electron number density, combined with the ionization parameter, indicates an outflow distance of approximately 2.2 kpc from the central source. Having a mass outflow rate of more than one thousand solar masses per year and a kinetic energy output exceeding 5% of the Eddington luminosity, this outflow can significantly contribute to AGN feedback. Conclusions.Our findings suggest the absorption outflow in J1402+2330 plays a potentially significant role in AGN feedback processes. This study highlights the value of DESI data in exploring AGN feedback mechanisms. 
    more » « less
  5. ; ; ; ; ; (, Journal of Electric Propulsion)
    Abstract A key issue in the development of theory and models for plasma propulsion devices is to describe the instabilities and fluctuations of the devices. It has been widely recognized that many Hall effect thrusters (HETs) exhibit oscillations at frequencies in the range of ∼ 20 kHz. These ionization-related oscillations are generally referred to as Breathing Mode oscillations and have been the subject of considerable research. Here, for the first time, we report direct temporally resolved measurements of the ground state neutral density variation during the period of the oscillation. We used the laser-based Two-Photon Absorption Laser Induced Fluorescence (TALIF) technique to measure neutrals within the plume of a 1.5 kW HET operating on krypton (Kr). Our TALIF scheme employs a frequency-doubled, pulsed dye laser operating at ∼ 212 nm to probe ground state Kr atoms. A novel phase-binning approach is used to recover the time-dependent signal by assigning the timing of each collected TALIF signal (laser shot) relative to the phase of the discharge current. We find that the neutral density fluctuates quite strongly over the period of the oscillation, and that this fluctuation leads the current fluctuation as expected. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email