Same enhancement exponents as in Fig. 1, but with other approximations. Solid, dotted, and dot-dashed lines correspond to results while neglecting ionic quantum effects on the enhancement factor: the dotted line corresponds to the LMR for OCP (Eq. (12)), the dot-dashed line demonstrates LMR for the polarizable electron background (Eq. (11)), and the solid line shows h₀ beyond the LMR approximation (Eq. (19)). The dashed lines illustrate the impact of ionic quantum effects: the long-dashed line presents the fit of Chugunov & DeWitt (2009a), while the short-dashed line is the approximation qh₀, which includes both the ionic and electronic screening contributions and takes both the quantum effects and the deviations from the LMR into account (see text).