Simultaneous Excitation and Ionization of Argon by Electrons to the Upper Laser States ofAr+

Abstract

Experimental cross sections for the simultaneous excitation and ionization of argon to the 4P configuration of Ar' are presented. The data are found to be in considerable disagreement with previous work. Optical excitation functions for the important argon-ion laser lines are given, and the results are compared with the observed relative gains of the lines in a pulsed laser. The cross sections for excitation to the 4P P states of Ar+ are found to have an E dependence with energy in the range 250 -700 eV, in disagreement with the asymptotic behavior predicted from the sudden approximation.

The use of Langmuir probes and optical emission spectroscopy to measure electron energy distribution functions in RF-generated argon plasmas

“…In figure 9, lg(@+) is also plotted against pressure where it can be seen that @+ increases more rapidly with reducing pressure than does @' . The cross section (a+) for the transition (4P5,2 + 4p 4P5/2), in the argon ion has a threshold energy ( E ; ) of 35 eV (Latimer and St John 1970) which increases to a maximum value of 6 X 1O-l' cm2 at an electron energy of 54 eV. The pressure dependence of @+ therefore indicates that the proportion of electrons with an energy greater than 35 eV increases as the pressure is lowered.…”

Application of excitation cross sections to optical plasma diagnostics

“…Extensive measurements have been made for the simultaneous ionization/excitation of Ar into the levels of the 3p 4 4p configuration of Ar + [23][24][25][26][27]. Limited measurements have also been taken for selected transitions from levels of the 3p 4 4d [26] and 3p 4 5s [24] configurations.…”

“…Extensive measurements have been made for the simultaneous ionization/excitation of Ar into the levels of the 3p 4 4p configuration of Ar + [23][24][25][26][27]. Limited measurements have also been taken for selected transitions from levels of the 3p 4 4d [26] and 3p 4 5s [24] configurations. As is evident in figure 1(b), the optical emission cross sections at 50 eV for many of the 3p 4 4p → 3p 4 4s transitions (420-490 nm) are larger than all but the 2p → 1s transition array.…”

A simulation of electron motion in the cathode sheath region of a glow discharge in argon

“…Consequently, the partial cross sections of Schram (1966) have been re-evaluated to remove the contribution made by these inner-shell processes, and are then used to determine the coefficients v , and 8 given in equation (3) for the high-energy region E > 500 eV. For simultaneous excitation and ionisation of argon atoms leading to the production of the AT+* species, the cross sections have been formulated using the experimental data of Latimer and St John (1970) in the low-energy region E < 200 eV, and are constrained to decrease as (In E ) / E in the highenergy region ( E > 1000 eV) in accordance with the theoretical predictions of the 'sudden perturbation' approximation of Koozekanani (1966). Of the AT+* states known to be pumped by direct electron impact, only those levels with cross sections greater than 0.5% of that for M-shell ionisation are considered.…”