Kinetic energy focusing for pulsed ion desorption mass spectrometry

The present invention relates to a means and method for decreasing the energy distribution of ions produced from solid or liquid samples by pulsed desorption method. More particularly, the present invention discloses a method wherein the kinetic energies of ions are related to their locations at a given time after the excitation event which caused their desorption. Based on this relationship between ion position and energy, an accelerating electric field is applied at a predetermined time after the excitation event. The magnitude of the applied electric field and the time of its application are such that the kinetic energy distribution of the ions is substantially reduced or eliminated.