Measurement of electron-impact excitation into the3p54plevels of argon using Fourier-transform spectroscopy

Abstract

To experimentally determine electron-impact excitation cross sections with the optical method, it is necessary to measure all transitions out of a level ͑the apparent cross sections͒, as well as the cascades into the level. In the case of the ten 3p 5 4p levels of argon, the emissions to lower levels lie in the visible and near infrared ͑660-1150 nm͒ and are hence observable with a monochromator-photomultiplier-tube ͑PMT͒ system. A Fourier-transform spectrometer ͑FTS͒ allows us to measure the previously uninvestigated cascades that lie in the infrared. For the incident electron energy range between onset and 300 eV, we have measured the apparent cross sections with a monochromator-PMT system, and the cascade cross sections with a weak emission FTS system. The magnitude of both the apparent and cascade cross sections increases with target gas pressure due to radiation trapping effects. By subtracting the cascade contributions from the apparent cross sections, we have determined the direct cross sections and verified that they do not vary with pressure in the 0.5-4-mTorr pressure range considered here.

Use of particle-in-cell simulations to improve the actinometry technique for determination of absolute atomic oxygen density

“…As argon is an atomic gas there are no dissociative excitation channels available, so the argon line width should serve as a good indicator of gas temperature. Comparing the emission widths for the profiles in figure 5 [30,31,16]. The results of the experiments are shown in figure 6 below.…”

Diagnostic-based modeling on a micro-scale atmospheric-pressure plasma jet

“…The thresholds for direct electron-impact excitation of O(3p 3 P) at 10.98 eV and of Ar(2p 1 ) at 13.48 eV differ by 2.5 eV according to the cross-section data [26][27][28]. At atmospheric pressure, however, this small threshold difference has a significant influence on the excitation rate ratio due to considerable variations of the electron energy distribution in this energy range.…”

“…The emission is determined by multiplying the simulated electron-impact excitation coefficient of the Ar(2p 1 ) state with the time-and space-dependent electron density and integrating the resulting time dependence to account for the effective lifetime of the upper state. Cascade processes populating the Ar(2p 1 ) state are in general comparatively small [26]. At atmospheric pressure, cascade processes can be assumed to be even smaller due to very effective collisional quenching of the upper level.…”

Phase resolved optical emission spectroscopy: a non-intrusive diagnostic to study electron dynamics in capacitive radio frequency discharges

“…For this analysis an adequate ansatz for the EEDF depending on the individual discharge must be made and the cross sections for electron impact excitation from the ground state must be accurately known for all energy levels involved. For rare gases such as argon, neon, krypton, and xenon these cross sections are provided by Lin et al [32][33][34][35][36]. Small amounts of such rare gases are typically admixed as tracer gases for PROES, since they are little intrusive.…”