  We study collision processes of moving breathers with the same frequency,
traveling with opposite directions within a Klein-Gordon chain of oscillators.
Two types of collisions have been analyzed: symmetric and non-symmetric,
head-on collisions. For low enough frequency the outcome is strongly dependent
of the dynamical states of the two colliding breathers just before the
collision. For symmetric collisions, several results can be observed: breather
generation, with the formation of a trapped breather and two new moving
breathers; breather reflection; generation of two new moving breathers; and
breather fusion bringing about a trapped breather. For non-symmetric collisions
the possible results are: breather generation, with the formation of three new
moving breathers; breather fusion, originating a new moving breather; breather
trapping with also breather reflection; generation of two new moving breathers;
and two new moving breathers traveling as a ligand state. Breather annihilation
has never been observed.
