Trigonometric mapping for the electric field strength in molecular optimal control theory

In molecular optimal control theory a laser pulse is designed to drive a molecular system to a target value of an observable. To be feasible in the laboratory, the optimal electric field must have a finite amplitude. Current algorithms limit the maximum amplitude indirectly by constraining the field's energy. We introduce a trigonometric mapping for the field amplitude to limit the maximum amplitude explicitly. In a calculation with hydrogen fluoride we show that an explicit amplitude constraint is particularly important when we account for the electric field's effect on the electronic structure.