Electron impact ionization is a process where high-energy electrons collide with neutral atoms or molecules, causing them to lose one or more electrons. This collision results in the formation of positively charged ions and free electrons. The energy from the incoming electron must be sufficient to overcome the binding energy of the electrons in the target atom or molecule. This technique is commonly used in mass spectrometry and other analytical methods to identify and quantify substances. By analyzing the resulting ions, scientists can determine the composition and structure of various materials, making electron impact ionization a valuable tool in chemistry and physics.