Monitoring active species in an atmospheric pressure dielectric‐barrier discharge: Observation of the Herman‐infrared system

Abstract

An electronic and spectroscopic study of dielectric-barrier discharge transition from the Townsend to the filamentary mode is presented. The discharge is generated under pure nitrogen flow at atmospheric pressure in a reactor with parallel configuration of cylindrical electrodes covered with Al 2 O 3 dielectrics, applying a frequency of 4.85 kHz. The goal of the study was to find optimal conditions for observation of the Herman-infrared (HIR) transition (C" 5 Π + u → A' 5 Σ + g ) in a perspective to develop and test a ro-vibrational model for this quintet band. We have focused on finding the maximum emissivity of the HIR transition in the homogeneous discharge regime as it offers a more suitable source for calibrating the HIR model. Besides the capability of generating a spatially homogeneous type of radiation, our discharge design also allowed the observation of HIR without detectable interference from the first positive system of nitrogen which is not common for atmospheric pressure discharges. In the study, a time-resolved observation of the NO system, the second positive and the HIR nitrogen systems were performed and their emissivities analysed as a function of the discharge period and power. The optimum for the observation of the HIR system was found at 2.94 W (power density of 6 W/cm 3 ), corresponding to the Townsend discharge just before its transition to the filamentary one. KEYWORDSdielectric-barrier discharge, Herman-infrared system, nitrogen, optical emission spectroscopy, Townsend atmospheric discharge 1

Untangling the Herman-infrared spectra of nitrogen atmospheric-pressure dielectric-barrier discharge

“…The first task was realized by coupling the PGHOPHER simulation package [35] with the molecular constants obtained from the high-resolution experiments [22,26]. The second part consisted of comparing this model to the experimental DBD spectrum recorded using a Mechelle spectrometer coupled with a gated detector [1]. Analyzing the spectrum (figure 7), we have shown that there is a part of the HIR spectrum unaffected by the 1PSpresence or the Mechelle diffraction order crossings.…”

“…As mentioned in the introduction, the main criterion for selecting a discharge for the benchmark of the HIR simulation was the capability of producing an HIR spectrum with In [1], we have deduced that the optimal conditions for the observation of the HIR in pure nitrogen at atmospheric pressure (1600 sccm of flow) were at the maximal power of a Townsend regime, at 2.94 W (power density of 6 W cm −3 ), right before passing to the filamentary mode. The maximum HIR emission occurred around 125 μs of time regarding the discharge period.…”

“…In our previous paper [1], we reported on the experimental conditions of an atmospheric-pressure nitrogen dielectric-barrier discharge (DBD), at which the emission of the first positive system (1PS) was suppressed and thus offered remarkable conditions for the observation of the Herman-infrared (HIR) system. As a consequence, we were able to record sufficiently resolved and developed ro-vibrational spectra suitable for bench-marking the theoretical model for the synthesis of the complex HIR emission spectra described hereby.…”

“…Following this introduction, the paper continues with the description of the ro-vibrational model of the HIR system in section 2. The experimental setup, widely discussed in [1], is briefly summarized in section 3. Section 4 describes, in detail, spectroscopic analysis of the recorded DBD spectra.…”

Estrutura eletrônica, espectroscopia e dinâmica quase-clássica de sistemas moleculares: um estudo teórico

“…De acordo com nossos resultados, as bandas de emissão do sistema C ′′5 Π u → A ′5 Σ + g podem ser encontradas no intervalo de 700-900 nm. Segundo Annušová et al [206] e Čermak et al [203] obter espectros puros de HIR, ou seja, livres da interefrência do sistema de bandas primeiro positivo (B 3 Π g → A 3 Σ + u ) não é uma tarefa das mais fáceis, desde que as bandas com maiores probabilidades de transição deste sistema encontram entre 600-800 nm. Esta situação está bem representada na Figura 5 da Ref.…”