State-by-state emission spectra fitting for non-equilibrium plasmas: OH spectra of surface barrier discharge at argon/water interface

Abstract

Abstract. Optical emission spectroscopy applied to non-equilibrium plasmas in molecular gases can give important information on basic plasma parameters, including the rotational, vibrational temperatures and densities of the investigated radiative states. In order to precisely understand the non-equilibrium of rotational-vibrational state distribution from investigated spectra without limiting presumptions, a state-bystate temperature-independent fitting procedure is the ideal approach. In this paper we present a novel software tool developed for this purpose, freely available for scientific community. The introduced tool offers a convenient way to construct Boltzmann plots even from partially overlapping spectra, in user-friendly environment.We apply the novel software to the challenging case of OH spectra in surface streamer discharges generated from the triple-line of argon/water/dielectrics interface. After the barrier discharge is characterised by ICCD and electrical measurements, the spatially and phase resolved rotational temperatures from N 2 (C-B) and OH(A-X) spectra are measured, analysed and compared. The precise analysis shows that OH(A) states with quantum numbers (v = 0, 9 ≤ N ≤ 13) are overpopulated with respect to the found two-Boltzmann distribution. We hypothesise that fast vibrational-energy transfer is responsible for this phenomenon observed here for the first time. Finally, the vibrational temperature of the plasma and the relative populations of hot and cold OH(A) states are quantified spatially and phase resolved.PACS numbers: 52.30.-q, 52.50. Dg,

Design and evaluation of plasma polymer deposition on hollow objects by electrical plasma generated from the liquid surface

“…A schematic diagram of the experimental assembly and images of the generated electric plasma are shown in Figure a‐h. In principle, the SDBD is generated due to high electric field generated in our case by the triple point effect at the common line between air, liquid electrode surface, and tube wall surface . Detailed description and some characteristics of this type of electric discharge can be found in the work of Galmiz et al Technically, any electrically conductive liquid can be used as the liquid electrode, but from the practical standpoint, low conductivity of solution leads to heating of the liquid electrode.…”

Editorial for plasma diagnostics using spectroscopic methods

“…However, in atmospheric-pressure plasmas, we sometimes observe an optical emission spectrum which cannot be fitted by a Boltzmann distribution corresponding to a rotational temperature. To solve the problem in the spectral fitting, Vorac et al developed a state-by-state fitting method and applied it to OH spectra observed in a surface barrier discharge [2].…”

Laser-Induced Fluorescence of Hydroxyl (OH) Radical in Cold Atmospheric Discharges

“…Consequently, neither the N nor the J quantum number is considered "good," but both are "almost good" and can be used to label the rotational states depending on the preference. 1 The relation between the two is J ¼ N AE 1=2 for the fine-structure components, usually labeled 1 and 2, respectively. See Table 1 for summary of the quantum numbers.…”

“…Here, we have used the standard spectroscopic abbreviation: single prime (N 0 ) is used to describe the upper state of a transition (here exclusively the electronic state A) and double prime (N 00 ) describes the lower state (here exclusively the X electronic state). 1 In this text, we adopt the newer notation with J for the quantum number describing the total angular momentum (apart from the nuclear spin that will be neglected in the whole chapter), N for the total angular momentum apart from the electronic spin, R for pure rotation (seldom used), and S for angular momentum of electronic spin, as in [12,13]. In Herzberg's book, the same quantum numbers are called J, K, N , and S,respectively .…”

“…Even though the hydroxyl (OH) in laboratory discharges readily emits radiation, which may be the source of many interesting information [1], there is no known direct and reliable method of determining the total OH radical density from the emission spectra. Indeed, the radicals in the ground electronic states are usually the most abundant and their effect on the plasma chemistry is dominant, but they are not observable by simple emission spectroscopy.…”