A theoretical approach based on molecular orbital theory has been provided. By applying this theory to a bond-breaking process, the ionization probability of Cu adsobates sputtered from a “5×5”-Cu/Si(111) surface has been studied. Three important aspects have been confirmed: (1) importance of a long range electrostatic potential such as the image potential, (2) importance of the coulomb repulsive potential between the Cu 4s spin-up and spin-down electron, and finally (3) acceleration and deceleration effects depending on charge state, which is a result of the interplay of the molecular bonding interaction and the long range electrostatic interaction. The measurements of ionization probability will provide us more information of the adiabatic potential curves of the reactants from the surfaces.