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 1s 2l towards the fundamental level 1s 2 1 S 0 , like appropriate lines. More precisely, the line of resonance w due to the transition 1s2p 1 P 1 --- 1s 21 S 0 , the line of intercombinaison (x,y) 1s2p 3 P 2,1 --- 1s 21 S 0 as well as prohibited line z due to the transition 1s 23 S 1 --- 1s2 1 S 0 . These lines appear clearly in the spectra of astrophysical plasmas. As helium-like ion, we chose two, the oxygen O 6+ (Z=8) and neon Ne 8+ (Z=10). We carried out calculations of the ration of lines intensity G=(z+x+y)/w of O 6+ and Ne 8+ according to the electronic temperature in the range going from 10 5 to 10 7 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.