Spectroscopic diagnosis in electronic temperature of photoionise plasmas

Abstract

In this work, we are interested in the diagnostics in electronic temperature of a plasma purely photoionized, based on the intensity ration of lines emitted by ions helium-like, which have an atomic number Z relatively small. We considered the three lines corresponding to the transitions starting from the excited levels 1s2l towards the fundamental level 1s^{2 1}S₀, like appropriate lines. More precisely, the line of resonance w due to the transition 1s2p ¹P₁ --- 1s²¹ S₀, the line of intercombinaison (x,y) 1s2p ³ P_2,1 --- 1s²¹ S₀  as well as prohibited line z due to the transition 1s²³ S₁ --- 1s2 ¹ S₀. These lines appear clearly in the spectra of astrophysical plasmas. As helium-like ion, we chose two, the oxygen O⁶⁺ (Z=8) and neon Ne⁸⁺ (Z=10). We carried out calculations of the ration of lines intensity G=(z+x+y)/w of O⁶⁺ and Ne⁸⁺  according to the electronic temperature in the range going from 10⁵ to 10⁷ K. We will see that, like it was shown by Gabriel and Jordan in 1969 [1], this intensity ration can be very sensitive to the temperature electronic and practically independent of the electronic density. Consequently, the ration G can be used to determine in a reliable way the electronic temperature of plasma observed [2].

Keywords: Strongly charged ions, lines emission, radiative and dielectronic recombination.