Rate coefficients for populating excited levels of He-like ions by inner-shell ionization of Li-like ions

Simple expressions that include intermediate coupling mixing effects are given for the cross sections and rate coefficients for populating the singly excited levels of He-like ions through the process of inner-shell ionization of Li-like ions by electron impact. Illustrative numerical values for the rate coefficients for inner-shell ionization of several Li-like ions are given and compared with the rate coefficients for populating the same upper levels by the alternative mechanism of electron impact excitation from the ground level of the He-like ions. For the temperatures at which the abundance of the He-like stage of ionization is a maximum, the inner-shell ionization rate coefficients increase relative to the excitation rate coefficients as the nuclear charge number Z increases. It appears that for all but very low Z, inner-shell ionization is an important mechanism for populating at least some of the excited levels of He-like ions. It is especially important for populating the (1s_1/22s_1/2)₁ or 1s2s ³S₁ level.