“…In the case of t-steps, these are particle creations in a constant uniform electric field [5][6][7][8], in an adiabatic electric field [9,10], in the so-called T-constant electric field [18,19], in a periodic alternating in time electric field [9,10,20], in an exponentially decaying electric field [21], in an exponentially growing and decaying electric fields [22,23] (see Ref. [24] for the review), in a composite electric field [25], and in an inverse-square electric field [26]. In the case of x-steps, these are particle creation in the Sauter electric field [17], in the so-called L-constant electric field [27], and in the inhomogeneous exponential peak field [28] and inverse-square electric field [26,29].…”