I have a very complicated, long (thousands of terms) expression that boils down to a form of
expr = a1 Exp[b1] + a2 Exp[b2] + a3 Exp[b3]
Note that all a and b are huge symbolic expressions but the expression is expanded that way.
Now I would like to get a list with b1, b2, b3. All I can do is
but that does not give me a list.