Spectroscopic diagnosis in electronic temperature of photoionise plasmas
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 1s2 1S0, 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 P2,1 --- 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 , 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 .
Keywords: Strongly charged ions, lines emission, radiative and dielectronic recombination.