# How is energy transferred between atoms in a collision?

Consider two bare protons. One (A) is stationary (relative to some arbitrary massless observer); the other (B) is approaching A at 1 m/s. When they collide, I assume that they bounce.

What is the precise mechanism by which energy is transferred from A to B?

For bonus points: Is the mechanism the same if each proton has one electron (that is, a normal hydrogen atom)?

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I don't know if relevant to this particular scattering, but a normal hydrogen atom has one neutron too ;) –  Jorge Jan 26 '13 at 9:29
@Nivalth: The normal deuterium atom has one neutron, but the normal hydrogen atom doesn't. –  John Rennie Jan 26 '13 at 9:58