Transition from a state with a certain momentum into a state with a certain parameter of spinless particle escape in the external field

A distribution function on the parameter of escape of particle B with the amplitude of process A → B in the external stationary field is investigated in this work. This distribution function is directly related to the form factor of the external-field source. By way of illustration consideration has been given to a hydrogen-like atom. It is shown that the distribution into the forward hemisphere comprises information on the spatial structure of an electron cloud, while the distribution into the backward hemisphere reproduces a spatial structure in the vicinity of a nucleus.