Neutral and Excited Molecules and Atoms Densities in the Positive Column of Flowing N 2 DC Discharges
- PDF / 773,984 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 58 Downloads / 176 Views
GENERAL AND APPLIED PHYSICS
Neutral and Excited Molecules and Atoms Densities in the Positive Column of Flowing N2 DC Discharges Jacques Levaton 1
&
Aloisio Nelmo Klein 1 & Jayr Amorim 2
Received: 12 August 2020 / Accepted: 13 October 2020 # Sociedade Brasileira de Física 2020
Abstract We investigated flowing N2 DC discharges both experimentally and theoretically. The discharge gas and N2(X1Σ+g) vibrational temperatures, electron density (ne), reduced electric field (E/N), and radiative state densities were measured by optical emission spectrometry (OES) and Langmuir double probes. We formulated a discharge kinetic numerical model to calculate the densities of nitrogen species as functions of the gas residence time. We combine the experimental parameters measured in the discharge with the kinetic model to analyze different discharge conditions where E/N varies significantly. First, we analyzed the measured and calculated radiative states densities and N2(X1Σ+g) vibrational distributions at the end of the positive column. Results show good agreement between calculated and measured parameters. Then, we studied the excited molecular species densities, and neutral and excited atoms densities as functions of the discharge gas residence time. This work presents for the first time the temporal densities of excited molecular and atomic states from 10−9 to 10−1 s discharge residence times, calculated for experimental conditions where ne presents a low variation and E/N varies from high (94 Td) to relatively low values (48 Td). The discharge experimental conditions are discharge current of 60 mA, gas pressure of 230–530 Pa, and gas flow rate of 0.9 Slm−1. Keywords Neutral and excited atoms density . Neutral and excited molecule density . Nitrogen flowing discharges
1 Introduction Many fundamental aspects of the flowing N2 DC discharges have been evidenced worldwide, covering an extensive set of their properties as the electron energy distribution function (EEDF), N2(X1Σ+g) vibrational distribution (VDF), electronswarm properties, electron excitation rate constants, and species densities [1–7]. In our knowledge, only the Indian team [5, 6] studied theoretically the temporal evolution of the density of excited molecular states in the N2 discharge. They studied some excited molecular species densities for discharge residence times ranging from 4 × 10−4–10−1 s for a discharge with E/N = 50 Td and ne = 8 × 1010 cm−3. Recently, we studied short residence time nitrogen discharges operating at different
* Jacques Levaton [email protected] 1
Laboratório de Materiais (LABMAT), Universidade Federal de Santa Catarina, Florianópolis 88040-900, Brazil
2
Departamento de Física, Instituto Tecnológico de Aeronáutica, São José dos Campos 12228-900, Brazil
discharge currents (10–50 mA) [8]. We calculated the neutral and excited molecular and atomic densities for the experimental conditions. These conditions represented discharges operating at high E/N values (90–118 Td), ne varying from 1010 to 1011 cm−3, and discharge resid
Data Loading...
