Eur. Phys. J. Appl. Phys.
Volume 43, Number 1, July 2008
|Page(s)||93 - 102|
|Section||Plasma, Discharges and Processes|
|Published online||30 May 2008|
Absolute intensity calibration of emission spectra: application to the forbidden 346 nm nitrogen line for N(2P°) metastable atoms density measurement in flowing afterglow
Department of Physics, Iran University of Science & Technology, Narmak, Tehran, 16846-13114, Iran
2 Laboratoire de Spectrométrie Physique, Université Joseph Fourier de Grenoble & CNRS, 38402 St Martin d'Hères, France
Corresponding author: Nader.Sadeghi@ujf-grenoble.fr
Revised: 11 March 2008
Accepted: 28 March 2008
Published online: 30 May 2008
A novel method, based on emission signal from the excitation transfer reaction: Ar*(3P2) + N2(X) N2*(C3) + Ar, is proposed for the intensity calibration of the spectroscopic optical detection system in absolute scale. It is applied for the measurement of N(2P°) metastable atoms density in the Short Lived Afterglow (SLA) of a 440 Pa nitrogen discharge produced by a 433 MHz resonant cavity. This density is deduced from the absolute intensity of the forbidden N(2P°–4S°) line at 346.65 nm, whose transition probability is only 0.005 s−1. The N(2P°) density variation in the SLA resembles those of N2(A3 ) metastable molecules and electrons or the emission intensities of first positive (1+), second positive (2+) and first negative (1−) systems of N2. It first decays after the discharge zone up to a minimum and hence increases by almost a factor of thirty to reach a maximum value of 6 × 1017 m−3 at the maximum of the SLA. It is proposed that N(2P°) density results from a local equilibrium between its production: N2(A3) + N(4S) N(2P) + N2(X1, v) and loss: N2(X1, v ≥ 10)+ N(2P) N2 (A3) + N(4S) reactions, which strongly couple the atomic and molecular metastable states and hence recycle N2(A3) metastable molecules produced in the SLA. The balance equation of N(2P°) density provides a N2(X1; v ≥ 10) density of 6.5 × 1020 m−3 at the maximum of the SLA. This corresponds to 1% of the total N2 molecules in vibrationally excited levels v ≥ 10.
PACS: 52.20.Hv – Atomic, molecular, ion, and heavy-particle collisions / 33.70.Fd – Absolute and relative line and band intensities / 52.70.Kz – Optical (ultraviolet, visible, infrared) measurements
© EDP Sciences, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.