We consider weakly dissipative perturbations of Hamiltonian systems of
the form where V is a three times differentiable 2 pi-periodic functi
on, with two maxima and two minima per period. The dissipation is para
metrized by d > 0 and as d --> 0 the system tends to the Hamiltonian s
ystem. With the addition of dissipation, the system develops a pair of
attractors, B and D (module the periodicity in x), one near each of t
he minima of V. We show that for typical systems these can be chosen s
o that as d --> 0 there exists a countable set, J(k), of non-trivial d
isjoint intervals accumulating on zero from above such that if d is an
element of J(k) then no solutions with sufficiently large initial ene
rgy and initial velocity of a given sign can be attracted to D (i.e. a
lmost all such solutions tend to B, independent of the initial speed).