Modelling of processes responsible for nonlinear absorption of UV laser radiation in ionic crystals

Two models of interaction of UV and VUV laser radiation with MgF$_2$, CaF$_2$, and BaF$_2$ crystals are considered. In the first version, the laser radiation wavelength falls into the absorption region of $F$-centres, in the second version it is located in the short-wavelength region of the $H$-centre absorption wing. The photodissociation of $F_2^-$-complexes in crystals into two holes is shown to be an efficient mechanism of defect formation in the crystal structure. The consideration of these and other processes of relaxation of electronic excitation allows one to explain many experimental effects produced by ionising and laser radiation in ionic crystals.