An electron in the presence of multiple zero range potentials and an external laser field -- exact solutions for photoionization and stimulated bremsstrahlung

The method of zero range potential (ZRP) for one-electron problems is reviewed. In the absence of an external electromagnetic field, the notion of a ZRP is introduced from different points of view and for an arbitrary dimension of space. Then, three-dimensional problems of motion of an electron in the field of several ZRPs and laser radiation are studied. Exact wave functions for the processes of photoionization and stimulated bremsstrahlung in the presence of the laser field of an arbitrary pulse shape are obtained in the form of one-dimensional integral representations.