A question about quantum tunnelling

[Shyan]

I understand quantum tunnelling while thought as the one happening in fusion.But could someone explain the proccess when we're talking about a particle passing through a physical barrier not just a potential barrier?
thanks

[Drakkith]

ALL barriers are potential barriers. The repulsion of a proton against a nucleus for fusion is just like the repulsion of an atom against other atoms as it tries to get through whatever barrier.

[Shyan]

Yes I understand that but there is difference between these two situations.
In fusion a proton goes into the high potential area of the electric field and continues motion till it collides with the other proton and its finished.
But in second situation the atom not only must go into the high potential area but also must pass the atoms themselves.How can matter pass through matter?
that's what I mean.(nice signature drak)
thanks