Calculation of the relative abundance between He-like and Li-like Cr under coronal conditions

The paper provides details of theoretical calculations of the relative abundance between He-like and Li-like Cr in the electron temperature range from 0.1 to 20 keV under coronal conditions. The results show that the abundance of Li-like Cr is less than 10.4% when the election temperature exceeds 3 keV and this percentage will further decrease when photon ionization is taken into account. Thus, it is proven that for the Cr plasma it is approximately true that there are only two charge states (H-like and He-like) in the plasma when the electron temperature is beyond 3 keV The results also show that the abundance of Li-like Cr will reach a maximum in the temperature range from 0.8 to 0.9 keV. In this paper the Younger formula is used to estimate the electron-ion collision rates and it is shown that this formula is in good agreement with the experimental data and is better than other theoretical methods. Dielectronic recombination of He-like Cr is considered by a full-quantum-mechanics method and the total electronic recombination rates of He-like Cr will reach a maximum value at a temperature of 3.5 keV, which is near the plasma temperature 3 keV formed as in Shepard et al (1996 Phys. Rev. E 53 5291)