As stated above, various mechanisms of EDSR operate in different crystals. The mechanism of its generically high efficiency is illustrated below as applied to electrons in direct-gap semiconductors of the InSb type. If spin–orbit splitting of energy levels Δ Δ s o is comparable to the forbidden gap E G , the effective mass of an electron m ∗ ∗ and its g -factor can be evaluated in the framework of the Kane scheme, see k·p perturbation theory.