  The head-on collision of ion-acoustic solitary waves in a collisionless
plasma with cold ions and Boltzmann electrons is studied. It is shown that
solitary waves of sufficiently large amplitudes do not retain their identity
after a collision. Their amplitudes decrease and their forms change.
Dependences of amplitudes of the potential and densities of ions and electrons
after a head-on collision of identical solitary waves on their initial
amplitude are presented.
