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

Abstract

This study presents the first application of the N 2 Herman-infrared (HIR) ro-vibrational model for the metrology of the atmospheric-pressure dielectric-barrier discharge. Our recent findings of suitable conditions for observation of the unperturbed HIR system (Annušová et al Contrib. Plasma Phys. 2017) gave us the opportunity to develop and test a numerical representation of this complex system composed of 75 branches. Commonly, the HIR covers a part of the near infrared spectra (690-850 nm) with its bands mixed with the N 2 first positive system (1PS), which hinders applications of these systems for optical metrology of the discharge. In this work, we present a complex ro-vibrational model of the 1PS and HIR systems, which allowed us to untangle their spectra and retrieve the rotational temperature and vibrational populations of the systems for the first time. The latter was achieved by coupling the PGHOPHER simulation package with molecular constants obtained from high-resolution experiments. To test the model, the results and precision were compared to the retrievals based on the models of the NO γ and N 2 second positive systems using the LIFBASE and SPECAIR programs, respectively.

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

“…Sobre este tópico, as condições as quais Herman observou 8 bandas do sistema HIR foram (i) baixa corrente de descarga e (ii) nitrogênio puro a temperatura de 77 K [202]. Com o advento de novos aparatus experimentais, Čermak et al [203] propuseram outras circunstâncias as quais julgam ser "ideais" na observação deste sistema. Além do mais, identificou-se que as transições vibrônicas entre as bandas (v ′ , v ′′ = 0) são as mais intensas e devem ocorrer próximo de 800 nm.…”

“…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.…”